Error Messages Parallels 4 - can't open VM

When trying to open my Parallels virtual machine to do some work in Windows, I get the following error message.......

- Unable to load the Parallels driver - restart your Mac and try again.

I click OK and then get the message - Unexpected error occured while starting the virtual machine. Contact Parallels support for assistance.

I click OK and tried restarting the computer and end up going around in circles with the same error messages.

I'm using Parallels 4 and Mac OSX 10.6

Thanks for any help you can offer!
Sheila

 

Please make sure you have the latest build of Parallels Desktop 4 installed: http://kb.parallels.com/en/5802