I have Ad Aware 6 and recenty installed SpyBot S&D along with ZoneAlarm. SpyBot ran great for about a week but now it hangs when trying to remove the stuff it detected and I have to ctrl-alt-del. It shows it "not responding" so I don't know if I would recommend SpyBot or not.
Just a suggestion- your installation may be corrupted, either from malware ( many have code that jams up protective software ) or the orneryness associated with Windows- try uninstalling and a fresh reinstall from another download.
I had an ad-aware problem just two days ago. Loaded the new Ad-Aware SP and it works fine.