Weird Connection Problem

For the first time ever, I'm having connectivity issues.
On my main computer (a desktop connected via ethernet cable to router) I cannot connect to the internet all of a sudden.
1) all my other devices - laptops, other desktops, iPads, etc - connect fine via the same router
2) I can connect OK on the same computer when I boot into OS X.
3) if I do a 'troubleshoot connection problems', just says 'cannot identify the problems'
4) the network connection icon on the notification area says 'Internet access'.
But, when I load IE or safari then I just get the 'cannot display the web page'.
What on earth could be wrong here? Virus? Something obvious?

OK, did a system restore and everything is fine now.
Convinced it was a virus, because there was a weird exe in the notifications area about virus scanning.
Oh well, all's well that's ends well!