After reverting back from 11992 to 11828, I gave 11994 a try. Was a nightmare. Dozens of processes inside my XP SP 3 VM not starting including the explorer itself rendering the VM completely useless. Tried a series of Prallels tools deinstall + reinstall, additionally completely removing the Parallels host application for clean reinstall. Reached a relatively stable situation now, but every second or third startup, I have to restart the VM again because still processes are hanging. When the startup completes successfully there are no problems. Anybody else with similiar experiences?
Update: Spent some hours to completely remove any trace of Parallels tools including temp files, registry keys etc. and tried a clean install. Even removed 'dead' devices in the device manager that remained from previous installs. Seems there was a success. XP VM running stable since then with 11994. We will see how long this will last.
Didn't last very long - only a few starts later, a svchost process started amoking, followed by a torrent of other processes. VM is completely useless again. This is really a nightmare.