I had the exact same issue, and I have run Ad-Aware from Lavasoft early this morning and have not seen an ad or a highlighted word all day! It seems Ad-Aware fixed this, although it picked up a lot of false positives. I ran Ad-Aware at full scan settings, took like four hours to finish and wanted to reboot twice. Just a friendly tip for others with the issue coming here through google, maybe a mod can make my answer more professional looking ;)
Thanks a lot for all the advice you guys!
Edited by Orange Blossom, 22 February 2011 - 11:53 PM.