Roland. I am 99% sure that there has been a program installed on your machine by some rogue website.
I suggest that you hit "CTR-ALT-DEL" then look for programs that you don't know. "End task" them then see what happens.
I'd also search your HDD for any directories that were recently created and evaluate them.
This happened to me a while back and it was a ad delivery system that had been installed by a cr@ppy website.