Ditto for me. Continuous problems with three separate VMs running Windows XP. I made backups before the parallels upgrade (got bitten before). Tried restoring these multiple times, going through the Parallels Tools install. I've spent more time backing up and restoring VM's in the last week than doing any productive work.
One of the older VMs simply says it's corrupt and won't open no matter what I do. Thankfully I can use the mounter to still get to the files from the finder. Two of the VM's are clean XP builds I did in early January, so it's not like these are crufty old VMs with tons of legacy junk floating around. No virus software or anything that would tweak the Tools install on either of those.
The others complain about the audio controller not being able to be installed when Parallels Tools installs and updates, but if I boot the VM into safe mode, then run the installer it seems to work except various apps (notably Microsoft Visual Studio) choke and die as soon as they launch, and then subsequently the VM's won't boot.
Will try to track down a 11828 installer somewhere to roll back now and see if I can duplicate some of the success other members here have had.
Agree whole-heartedly with others observing that 11990 is whacked and should be avoided...