Problems connecting with Linksys WRT54G

Recently started having problems getting the router to work on 2 desktops - neither are wirelessly connected. The cable lights are on, the router lights are on, it shows on the computer that it is connected and even shows packets sent/received but I'm unable to access the internet. When I go to cmd and do ipconfig/all - one computer has a DHCP assigned whereas the other one is using a different address and is assigning it to several different applications. I have tried and tried to fix the problem, and tried power cycling both the modem and router but nothing seems to fix it. If you could give me some ideas on where to even start, I would be greatful. I'm not computer illiterate, but not savy either so if you need more info then please let me know.

I had the same problem with my router. There was a compatibility problem with my virus protection. I removed that virus protection and I had no problem getting on the net