I had that same issue!
I downloaded and ran CWShredder, Spybot and adaware and problem solved!!!
I run them all regularly now. You can google the names and they're all freeware and recommended. When I was having a problem, the "computer geeks" site recommended that these all be downloaded then ran on my computer in that order.
Also, my puter ran so much faster and cleaner.
Good luck!
KD