lepas,
Sounds like you might have a worm. Download AVG Free from the link below & see whether that helps.
http://free.grisoft.com/doc/2/lng/us/tpl/v5
Download it, update it, scan your computer & see if it finds a worm (Delf.ATB).

Search the forum & you'll see a few people have had this problem...AVG has fixed things for some

If you need more help, try one of the sites below.

http://www.spywarewarrior.com/index.php

http://www.castlecops.com/forums.html

http://forums.spywareinfo.com/index.php?showtopic=79038