It's hard to tell what's going on here, but I just upgraded to Parallels 7 on my 17" MBP running 10.6.8, and when I start Windows 7 (Ultimate, 64-bit, Boot Camp partition), the Parallels window will disappear and the icon will disappear from the Dock. If I re-launch Parallels, it appears to pick up again where it left off, but will only stay on the screen for another minute before it disappears again. The weird thing is, when I re-launch, the spinning dial re-appears like I'm launching it new. If I do a process listing, I see the same processes no matter if Parallels has been launched, has been launched and disappeared, or even if I've quit. What really sucks is, I can't keep Parallels up and running long enough on the screen to uninstall the extensions so I can downgrade to 6. What gives? BTW, this happens whether or not I've got my secondary display attached or not, am running Spaces or not.
I seem to be having the same problem (MacBook Pro, OS X 106.8, Parallels 7, Running Windows 7). I was able to make Parallels usable again by unplugging a USB display adapter I've been using to allow a 3-monitor (including the MacBook monitor) setup. The particular display adapter I'm using is the "Plugable UGA USB 2.0 Display Adapter", model "UGA-2K-A" (http://plugable.com/products/uga-2k-a/). Unplugging it seems to cause Parallels to function normally again.
