well, at first after installed dp4 I would just click the parallels icon and it would show up for a second then disappear. I just recently reinstalled parallels and now it opens, but gives me some virutalization error then won't start up.
These issues I was having on Parallels 6 since ML DP1, but didn't experienced any of these after updated to Parallels 7.
Are you sure you have latest version of Parallels 7?
Here's mine: https://skitch.com/unnamed-c8kc/eb1x1/about-parallels-desktop
T.