Main computer can't access internet suddenly

Hello, this evening my computer connected just fine to the internet. I went out with some friends, came home after a few hours and now the internet on my main computer will not work. I thought it was just not working in general but I tried my mother's laptop and ipo wirelessly and they can connect to he internet just fine.

Could I have a virus causing this or could my computer/router somehow have blocked access? The router connects to the desktop by ethernet and the ipod and laptop connect wirelessly. I've tried rebooting and restarting my computer/the router but nothing seems to be working and I'm perplexed as to what could have caused it.

I have tried using Chrome and Internet Explorer but FF gives me 'server not found', IE gives me 'cannot display page', whilst Chrome gives me 'this webpage can not be found, because the DNS lookup failed.'

I'd really appreciate if anyone has any insight to this.