The problem I was having with Avast (32 bit) was the auto-updater didn't work. Had to open the program from the start menu (not the notifier icon) and manually update definitions and software. I'll give it another try to see if they corrected the problem.
I read AVG Free will work, you just have to force it to install.
My SoundBlaster Live is in a drawer because it gave me so many problems, especially with HL2. I've been using onboard for a while.