Parallels Upgrade 4 to 5 Wont Start

After installing the upgrade mfrom 4 to 5 with the latest patch I can't start Parallels. It freezes on a grey screen as if it were booting but is actually hung up. I made no changes to anything on my machine prior to the upgrade.

I have an iMAC 27" 3ghz with 4GB machine with the 1TB drive.

I should mention I didn't uninstall 4 prior to the updrade just in case it loses all of my XP OS and files.