Bouncing screen

This problem has corrected itself but I wonder if anyone else
has experienced this.
For no particular reason my screen decided to start bouncing as
if I were moving the scroll bar up and down very fast (which I wasn't). It wouldn't respond to the cursor but would stop when the cursor was moved to the task bar.

I finally turned it off, using the button ( the only thing that worked) then back on and everything was back to normal.

Any ideas?

 

possibly a virus or spyware

suggest a scan
also lavasoft adaware

i had that on a friends XP machine, did a virus scan but nothing showed
- i promptly left the building LOL

 

Could it possibly have been a "joke file"?..I have seen files that make your screen bounce, melt, disappear...etc..