I recently downloaded Firefox 2.0.04 (upgrading from 1.5), and I kept getting error code 203 when trying to install add-ons. I've literally spent the last 4 days trying to fix this issue. Re installed a backup image, clean reinstalled Firefox about 50 times, including cleaning the registry of everything from Firefox; no fix. Someone recommended Filemon to moniter my profile folder. Sure as &^%#, Cyberhawk was messing with it. Uninstalling it solved the problem. I've seriously lost 5 years off my life trying to fix this problem! I have gray hairs now!