This could be a false alarm or a conflict between avast! antivirus and Ad-aware?
Most probably it's not a false alarm.
It's not a conflict either.
When Ad-aware tryed to get rid from the infection, avast! resident detected the file is being read.
Sometimes, if you find a virus keeps coming back after you delete it, disabling System Restore and rebooting could solve.
Other good things will be booting in Safe Mode (press F8 while booting) and running avast! from there.
Other, it's the boot time scanning.
Finally, use other antispywares (SpyBot, ewido, etc.) to scan your system.