Just to advise: I've used Norton 360 & Ad-Aware together for at least a year with no problems. Couple of days ago on start up my computer gave an error message that start up failed and an option to repair the problem automatically, which was done. All was ok afterwards except that Ad-Aware would freeze seconds into a new scan. (Deep scans by Norton 360, Threatfire, Malwarebytes and SpyBot found nothing.) Running Vista Home Premium on an Intel 2.50 Ghz Quad Core computer.

I finally traced the problem to Norton 360's Tamper Protecton feature. Disable Tamper Protection & the Ad-Aware scan will run. Enbled Tamper Protection & the scan hangs up quickly. (Of course, enable Tamper Protection again before hitting the internet.) To disable Tamper Protection on Norton 360 3.0; open 360, click on "settings" at the top & uncheck the Tamper Protection box on the right under Quick Controls. (The process also gives an option to automatically restore Tamper Protection after 15 minutes.)

If I didn't like Ad-Aware so much, I would not have gone to all of the trouble it took to track down this issue but running SpyBot in this problem hunt reminded me why I switched to Ad-Aware in the first place: It is quick, thorough & usually trouble free.