I can't really say if I started having problems when I upgraded to Parallels 7 or Lion as I don't use it often enough to have noticed. Currently running the latest version of Parallels 7 Desktop with Windows 7 64 bit and Lion. My Parallel Tools was the latest version as well, but I couldn't enter Coherence mode or access anything Mac from Windows. Parallel Tools was listed as being installed. Having scoured these forums I realised that my problem was with Tools and it was only partly a problem because the cursor would always flick from Windows to Mac without a problem. I had done everything, and I mean absolutely everything listed in these forums to uninstall Tools and reinstall. As Tools wouldn't show up in the Uninstall Programs control panel I did it manually and everytime I would try to reinstall from Parallels menu I would click the yes box when it came up and then nothing would happen. I have solved my problem by double clicking the prl-tools-win.iso located ~/Library/Parallels/Tools. I then put these files in a folder onto a USB flash drive and installed Tools into Windows 7 that way. The only other thing I did prior to this was install Windows Installer CleanUp Utility (which was another suggestion listed in these forums - didn't work for me) and ran this. As I don't have a great lot of files and programs on Windows I just selected all that was listed and removed it all. So far I haven't had to reinstall anything. Hope this helps some others out there having similar problems. I know it won't help all, but it might save someone from the utter frustration I was having with nothing working.
I strongly recommend to contact support team in such cases, or use www.kb.parallels.com. If you like to figure out the problem by yourself, please make sure you have a backup - you can make it from Virtual Machine menu --> Take a snapshot
A simple and effective answer I tried many more complicated solutions presented on the forum but this one worked fine. Thank you Margaret.
