Same thing happened to me and I tried virus scans and the works.
However on Friday the power was turned off because we were having some work done and then I had no connection to the net at all.
I found something had caused problems in my wireless router. I reset the router to the correct settings and everything is running really fast now.
The strange part was that was whatever caused the problem onlt affected some sites and not others. Anyway since I reset my router everything is flying along.
