My Windows 7 64 Bit (both Home Premium and Ultimate) running under Parallels Desktop 5 on my iMac i7 has been crashing after 5-10 minutes. Everytime! It could crash while using IE or any installed application in Windows. I've lost about 2 days solving this situation and I've found it. Everything stopped crashing and started to work perfectly only after I uninstalled Kaspersky Internet Security, which was suggested by Parallels. I have no idea what happened exactly, because I never had problems before. But the system could not work normally with this Kaspersky, so if you guys have regular app crashes in Windows 7 under Desktop 5, try removing Kaspersky stuff. Good luck!