Laptop can't find any networks

My boyfriend & I have been using the same modem (Motorola SURFboard) and router (Cisco WRT54G) with the same network setup for about six months now, living in the same apartment. The other day, he changed our router settings to enable wi-fi access with our Wii and DS's – after some trying, we got it working fine with all three game systems and both our computers. He was concerned about the security of WEP encryption and decided to be safe and change it back to WPA. After he did so, he was no longer able to get connected to our network with his laptop, which runs Windows 7. My XP desktop worked just fine – it was able to reconnect almost automatically since it had stored the old network settings. I can't say for sure if his did as well, but it seems more likely that he would have than not. Currently I have full access to our local network & the internet; authentication is set to WPA-PSK and encryption is TKIP. He's got his set up the same way, using the same network password and everything, but last night it wouldn't connect at all. He switched the authentication type back and forth a few times to test some things, but as of tonight it's not finding any networks at all. I reset the router and modem, his network adapter's been disabled, re-enabled, turned off at the switch, turned back on… All Windows diagnostics/troubleshooting report that either no networks could be found, or the adapter is switched off…even when it's not. Websites for the modem & router shed little light on the issue. I even tried using my USB wireless card with his laptop, but of course it needed to download a driver first. We're stumped at this point. It seems bizarre that it's working fine for me but not for him, but we can't figure out what setting might be different between the two stations. He tried to do a system restore to the day before we started changing things, but he was getting some errors and I'm not sure if it ever worked. Either way, he has absolutely no wireless access whatsoever. We haven't tried a direct wired connection yet, since his setup is a hassle to disconnect & reconnect, but if it would help anybody figure this one out, just say the word. Thanks in advance!

Hi, sorry to hear of the problems with your wireless set up
A good first step would be to connect the troublesome machine to the router with a cat 5e patch cable (network cable) and see if this assists in establishing an Internet connection.
You mention that:

We haven't tried a direct wired connection yet, since his setup is a hassle to disconnect & reconnect

just plug the cable in the router and in the computer…there should be no hassle.
Regards
paws

Try completely removing the existing Wireless network then create a new one:

See here: How to Remove a Wireless Network in Windows 7

There is most likely a disconnect in the encryption method/key. This should fix it.