Have IP but can't connect to internet

I have a Linksys SRX200 wireless router. HP computer running Windows XP.

I have been working on this problem for a day and a half and it's driving me batty.
My computer recently got hit with one of those viruses (or malware?) that pops up window that says your computer is infected with a virus and the only way to get rid of it is to purchase their antivirus application yadda yadda yadda and no matter what you do, you can't get rid of those pop up messages. I think you know the kind I"m talking about. So I did a system restore to the day before I got the virus and even tried a week before but since I've done the system restore, I cannot directly connect to the internet via a direct ethernet cable connection to the wireless routers ethernet port. I get the correct IP info, subnet, gateway, DNS info when I do an IPCONFIG but still can't connect to the internet. My wife and son can both connect to the wireless router and access the internet using their wireless connections. I am directly connected to one of the routers ethernet ports (there are 4) and still no internet. To confuse things even more, every once in awhile, I do connect to the interent and can browse for about 2 or 3 minutes then I totally lose the connection to the internet. Web pages won't display anymore. Yet all the IP info is accurate. I've rebooted the PC, modem, and router a hundred times. I've reset the router to factory defaults and re-established the wireless connection. I've done the IP release/flushdns/renew thing. I've swapped 3 or 4 ethernet cables with the same results. I have not tried directly connecting another computer to the router which is my next step. This will tell me if there is something wrong with my computer or the router I would assume.

I must add that the Port 4 link light on the router is always lit regardless of whether or not I have anything connected to it or not. If I connect my desktop computer to to ports 1 or 2 or 3, ports 1 and port 2 do not light up. Port 3 lights up when I connect to it but still no internet connection. When I use my wifes laptop which is connected wirelessly, I can browse to the router and log in but when I check the status of the ports, it says link is down for ports 1 thru 3. It says port 4 link is up, even though there is nothing connected to it. This does not change even when I reboot the router. I'm beginning to think I have a hardware problem with the ethernet ports on the router. If I take the router out of the equation completely, and directly connect my PC to the cable modem, I can get on the internet. I just don't recall whether I can continue to surf or if it too stops surfing after a few minutes or two. I'll have to try that tonight.

Lastly, I have looked up similar problems in this forum and have done the netshr commands, etc. but to no avail. I've disabled the firewall already also so that's not the problem.

Any suggestions are greatly appreciated.