New installs fail, existing installs hang during boot

I have Parallels 6 (latest version), iMac 27" Core i7, 8GB RAM. I have a Windows 7 VM that used to work fine. Now, every second time I try to boot it, it just hangs during boot (black screen) and need to shut down and try again. Or aero doesn't work. Or I get some service or process doesn't start error. Every friggin time. Usually, but not always, a restart brings it up Ok the second time.

I also install Windows 7 a lot (I use clean installs to test software). Every time I try a new install of Windows, I get an error during install that says Windows cannot be installed on this hardware! or a BSOD! Every friggin time! I have to try reinstalling a number of times before I achieve success. Unbelievably frustrating.

Other specs: Windows 7 Ult x64 install from .iso. I usually set 2GB RAM and 2 CPU cores.

I haven't tried reinstalling previous version of Parallels like other posts have suggested. Just wanted to vent my frustrations in case Parallels staff are watching.

 

The fix posted as a sticky at top of page seems to have fixed these issues, finally!