This is weird, cable modem seems to be screwing up the monitor

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Unfortunately I am the tech resource for not only my mother's computer
but my in-laws 'puter as well.
So I got called into my in-laws the other day and the weirdest thing is
happening.  They called me because their computer wouldn't boot up, or
sometimes it would and then it would shut down after a few minutes.

After fighting with the thing just to get it started and jumping
through various hoops I've discovered that the computer works fine as
long as the cable modem isn't plugged in.  The second I plug in the
modem the monitor goes all wonky.  So what the Hell would cause this?
They've been using this set up for quite a while with no problems.
Seems like most things started to go haywire when Ma in-law upgraded to
IE 7 (gee it couldn't be a Microsoft software causing problems could
it?) and also when she upgraded her AVG anit-virus program (or gee
could it be the freeware causing the problems?).
They did have both Norton and AV on the machine, but the problem
persisted even after I un-installed both of those.

My guess is it's a conflict of some sort.  But how do I find the
conflict without the modem being plugged in?

Could this be some kind of electronic noise issue coming from the power
cord for the modem or something?

What other things might cause this funky behavior?

Re: This is weird, cable modem seems to be screwing up the monitor

On 22 Nov 2006 16:02:40 -0800, wrote:

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If it is the *second* you powerup the cable modem, then I would assume
a ground loop or something.

I would get a power strip, get everyting plugged in there and try
again. If modem power plug is not keyed, and still have the problem,
rotate that plug 180 degrees and try again.
Still have the problem, drive over and swap or rent a new cable modem
from your ISP.

Re: This is weird, cable modem seems to be screwing up the monitor wrote:
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I'm writing mainly to clarify some ambiguities for the benefit of all. A cable
modem has 2 plugs to plugin: power & ethernet. Which? You probably mean power,
so are you unplugging the low-voltage at the CM or the 120v plug.

You say the monitor goes all wonky. :) Could you be a bit more descriptive?

Do you know how far the system was getting when it wouldn't boot up? Did it
POST? I suppose you weren't there at that time, but ask them what they had seen
on the monitor if anything.

The standard question. What, if anything. has changed? Hardware or software or
electrical cords and plugs?

Go into Control Panel - Power Options (that's the name in my Win2K) and disable
hibernate support. If it had been enabled, then reboot and try again.

Just some thoughts.


Re: This is weird, cable modem seems to be screwing up the monitor wrote:
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I'm also confused about some of the things you're saying, and some
clarification would be helpful. It does *seem* that you have an electrical
problem, not a computer problem, but that could just be because of the
ambiguity in what you're saying.

If it's not an electrical problem, and when you say "plug the modem in"
you're actually talking about connecting the Ethernet cable to the network
interface card, then you may have a bad NIC. If you're using a USB
connection from the modem to the computer, and things fail when you plug
in the USB cable, then get a real NIC. USB *can* be used for networking,
but it's nowhere near as efficient or reliable than using a real Ethernet
NIC, and should only be used if a NIC cannot be used.

Another possibility, but a long shot, could be bad memory chip, and the
problem is in the area used by the NIC or USB. But again, this is assuming
that you have a computer problem, and not an electrical problem.

Warren H.

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Re: This is weird, cable modem seems to be screwing up the monitor

Sorry I should have been more specific.

Yes, by plugging in I mean powering up.  The cable modem is connected
via ethernet, not USB.

As for how far the computer getson start up, it's usually starting
Windows when it shuts off.  If you think of the screen that comes up
showing "Windows XP" with the little status bar underneath that
repeatedly goes from left to right until the desktop appears it pretty
consistently completes the "left to right" sequence 7 times and then
shuts down (my father in law counted them).  I tried starting in safe
mode but got the same result.

By "wonky" I mean the picture on the monitor gets wavy and distorted
(colors out of phase).  It looks like interference, you know like in
the old days when you're TV wasn't tuned in properly.  I too thought it
was electrical, and I'm still open to that.  It just seems to weird to
start happening all of a sudden,when as far as I know, nothing's
changed in the way the equipments is set up.  I do wonder about the
house heat causing something, I may have to grill pop-in-law to see if
anything's changed along those lines.

Also that fact that it stops at the same point of start up almost every
time makes me think it's happening when Windows loads a driver or
allocates resources for the modem.  On the other hand every once in a
while you get through to the desk top and the icons load up, everything
looks good and then bam! it turns off.  So I'm getting some conflicting
results.  I tried booting off the XP disk, thinking that the monitor
driver file was corrupted somehow, but again it would shut down while
starting Windows.

I know enough to be dangerous, plus a little more as I sell software
for a living, but I'm pretty stumped.  I will bring my modem over
tomorrow and see what happens.  I may also lug a monitor over there
just to check everything-the monitor is a Dell made in 99.  I'm also
bringing my laptop,so I can get info from the net (you guys) while I'm
fighting it.  The modem does work fine on a laptop, so it's not
completely screwed.  I'm guessing that possibly somehow the anti-virus
program or IE upgrade changed the resource allocation and now the modem
and monitor are conflicting.  I have no idea why those programs would
do that, but I do know Microsoft seems to like to mess with as much of
the system as they can when they upgrade their stuff (especially IE).
It may have something to do with increased security.  I haven't seen
anything like this anywhere though.

Also I had them do a system restore to before the upgrades but that
didn't help.  I'll likely do that myself first thing tomorrow, pushing
it back until last week (there's nothing important on their computer
from that time period).  I'll probably spend most of my turkey day in
the computer room, but hey, it gets me away from watching the Lions

I appreciate any and all help you can give me.

Warren wrote:
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Re: This is weird, cable modem seems to be screwing up the monitor

On 22 Nov 2006 18:50:33 -0800, wrote:
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could be a component failure, or a ground gone bad,....

If you want to rule out your operating system download a knoppix iso
image, do a md5sum or sha1sum check, burn it and boot it.

Now you have a third party cd to check your hardware to rule out software.

Re: This is weird, cable modem seems to be screwing up the monitor

Bit Twister wrote:
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I tend to go with the power / ground loop issue. Or a bad Ethernet port
on the computer.

To try and isolate power, I'd put a switch in between the modem and
computer. (Or get a router. They SHOULD have one but that's another
story.) With modem off but router and/or switch on see what happens. Now
turn on modem. If "wonky" then it's in the modem. If not then the
router/switch is isolating the issue.

Assuming power I'd check for a bad ground at the cable entrance to the
house. Also unplug EVERYTHING else you have from your cable service. Try
another power strip and make sure the computer and modem are on the same
power strip.

It could also be a blown modem or bad power brick (if one) for the modem.

If not in their house / unit it could be something being done by a neighbor.

If the problem happens with just the router/switch turned on, very
likely your computer has a problem with it's Ethernet port.

Re: This is weird, cable modem seems to be screwing up the monitor wrote:
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Sort of. It's been accumulating dust all along and might have hit a critical
threshold. I say that because you haven't mentioned opening up the box and
blowing it out. You've mentioned Dell, so I suppose it has motherboard graphics,
but if it has an actual video card with its own cpu & fan, that could be clogged

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That would add to the problem per above.
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When restarting and as you would hit F8 to get the menu to go into Safe Mode,
enable Boot Logging instead, which I think will show the point of failure.

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Understand that you will not be able to use your modem for the internet as its
MAC Address is registered elsewhere. Its only help will be as an electrical
connection and I personally doubt that you have any problems in that regard.

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If that's the case, then it's obviously not screwed at all.

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Re: This is weird, cable modem seems to be screwing up the monitor

It seems to have beeen a bad NIC port on the MB.  Put in an old NIC
that I had laying around, disabled the port on the MB and everything's
good to go.  This should continue to work right?  Should I be concerned
about the rest of the MB going or is usually an isolated thing.  MB's
about 3 years old.

Thanks to everyone who replied.

Robert Heiling wrote:
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