I've had this problem with Beta 3, and then it went away. I started to get it again with Beta 3, and I saw that there was the RC out, so I thought that might help. It didn't. When I launch Parallels, the icon bounces for a while then stops. No window pops up, and no triangle shows up underneath the icon in the dock. Meanwhile, my computer becomes unresponsive. I can tell that the CPU is not always pegged, but the GUI feels like it is. I see in the Activity Monitor "Parallels Desktop (Not Responding)". I cannot use the AM to kill it. I am not able to reboot either. When I do, I get an error that Parallels Desktop won't quit. I've tried a kill -9. which seems to do more, but when I reboot after that, i get a blue screen with the chasing toothpick circle. The only way I have found to recover from this parallels launching hang is to hold down the power button which kills the machine. I have tried uninstalling and reinstalling, but that didn't help. To be clear, this is NOT when I start up a VM, this is when I start up Parallels. This happens before the user is prompted about which VM to load. Chris Machine Specs: MBP-DC 17" 2GB
May have solved my own problem. Seems to be related to USB. One of my USB drives wasn't fully "up" yet. I don't know why that might be a problem, but when I removed it from the machine, Parallels started up fine.