Problems with SMC Barricade 7004ABR

I've had an SMC Barricade 7004ABR for about 4 years now and have been quite happy with it. It sits between my DSL modem and my Windows XP Pro PC in my home/office and has kept me free of viruses for several years now.

For the last few days, I've been having Internet connectivity problems which I initially thought were weather-related. However, when I still had problems with connectivity today, despite rather good weather, I called my ISP, Sympatico, to work out the problem. We eventually got everything working again - I'm still not sure what was wrong in the first place - but discovered something rather interesting along the way: my Barricade has a considerable negative impact on my modem speed!

If I run the DSL modem directly to my PC, I get over 3.0 Mbps. If I run the DSL modem through the Barricade and then on to the PC, I get only around 1.3 Mbps. The friend who sold me the modem and helped me install and configure it said that was quite unusual and suggested I see if a firmware update helped the situation.

So, my first question: does it sound reasonable that the Barricade would have that significant an impact on my speed and that a firmware update might fix that problem?

I should mention that my speed has been well below the maximum as long as I've had the Barricade; it just never occurred to us that the Barricade could be hurting the speed.

My second and last question deals with the technique for applying the firmware update. On the assumption that the firmware update "couldn't hurt" the situation, I tried doing the update. I found this page, which lists the updates for my Barricade:

I downloaded the firmware update to my hard drive and unzipped it, then tried to apply the update from the SMC interface at http://192.168.2.1:88/tools_update.htm. The interface said that I still have V1.00, Firmware Date: 09-21-2001 on the Barricade, which I assume are the factory defaults. I clicked on Enter, then browsed to 7004ABR_FWv141004.dlf and clicked Start. I replied OK to the question: Do you wish to continue with the upgrade process? I replied OK to the warning that the Gateway may not respond to commands for a minute after the upgrade. Then I got this warning message: Upload Data Error! Please make sure your file is correct! and clicked OK.

I assume that clicking OK on that last error message aborted the attempt to install the firmware. The Update Firmware page still says Version 1.00, Firmware Date: 09-21-2001.

Is there something wrong with my technique or is the update file corrupt as the message seems to suggest? The .dlf file must be the correct file; the zip only contained three files and the other two were 'readme' files. Can anyone tell me how to get past this problem? I tried searching the FAQ at SMC but the database was down....

Or is the firmware update unlikely to help me in the first place?