Enabling encryption preventing laptop wireless internet access - help please!

I have had a wireless network set up between a laptop and my PC which has worked smoothly for a couple of weeks. Today when I booted up the laptop I got the message "Windows was unable to find a certificate to log you into the network " on top of my sys tray icon which now has a yellow triangle and exclamation mark on it!

I browsed about and discovered this was something to do with encryption. Up until this problem occuring I hadn't changed any of my router's (SpeedTouch

585) settings whatsoever or on the laptop. I tried putting in a brand new WPA-PSK key into the router then put it into the laptop, but still the same problem happens. I don't know is this is related but when I input the new key into the laptop in Wireless Network Connection Properties>wireless networks>properties>association hit ok then return to that window it has gone back to the router's default key, a 10 digit key which doesn't work. I also tried to repair the connection but that hasn't worked either.

I also read that if, in the network properties>authentication, the "enable IEEE 802.1x authentication for this network" box is enabled it can lead to connection problems. But it is unchecked. In fact, even if I wanted to enable it I can't because the entire box is greyed out. Can someone verify if this is where I can fix the problem, how this window came to be greyed out and how to fix it.

If I disable encrytpion on the router the laptop can connect to the internet no problem. I've tried a few keys, all generated by the online generator at

and it still won't connect with encryption enabled. The "certificate" notice just comes up again.

There are no viruses or malware on either machine, no new programs have been installed just prior to the problem occuring

So how has this problem occurred and how do I fix it?

Help gratefully received.

Harry

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