I think I have this same issue.
Lately, I noticed I get malware, that redirects me to fake websites while I browse. I installed clamtk and clamav, and it worked. But I recently updated eveything: the GUI seems nicer and there are more feature, but it doesn't work.
If I select a folder to be analyzed, an "Virus analyzer" window appears, freezes for few seconds, and then says that no menace was found. But it actually didn't analyze anything. I'm using trusty.
