I've got Vista installed on a Boot Camp and had the same problem when I booted it in Parallels Desktop 3.0.
It boots to the login screen then freezes, keyboard and mouse apparently not working.
I was about to give up and wait for a patch when I noticed that the hard drive icon on the Parallels status bar was going like the clappers.
I'm pretty used to Vista going very slowly every so often so decided to leave it for a while. I would hit a few keys and wiggle the mouse every so often. Eventually the keyboard started typing into the password box.
I logged in to Vista. They keyboard now seemed happy but the mouse was a no-go. Luckily I'm very used to working without a mouse in Windows so that didn't cause me a problem.
Slowly (very, very slowly) but surely Parallels Tools installed themselves. There wasn't much indication what it was doing other than the warning box you get telling you not to reboot. Every so often Windows would throw up an unsigned driver warning which I would except. After about a quarter of an hour it finished installing Parallels Tools.
The VM rebooted and it now all works (including the mouse).
It is still very very slow. I've not used Parallels for a few months due to the lack of Vista support, but I always found that when running a native Parallels VM it runs quickly but when running a Boot Camp installation under Parallels it is very slow. That was the case with XP, and seems to be still the case with Vista.
I'm going to boot up in Boot Camp mode next and disable Apple's keyboard manager thingie. It gets on my nerves anyway as it remaps a lot of the keys to places I can't find them!
With a bit of luck I might end up with a Vista install that works well in Boot Camp and Parallels. Or hell might freeze over.
