comment about troubleshoot guidance:
In order to reinstall Parallels Desktop you don't have to reinstall Windows - just download the latest PD6 build from KB http://kb.parallels.com/en/5802 and Click - Uninstall. Than open it once again and click Install.
In order to repar permissions - please open Disk Utility on Mac, click on Mac HD in the left panel of application and click on Repair Disk Permissions option.
Comment about PD upgrade - you still can download the free trial PD7 version and run it for up to 14 days in order to check if it fixes the issue
Last edited: Jun 24, 2012