Now it happend the second time after reinstalling OSX Tiger on my Macbook Pro: The installation of Parallels causes Spotlight not to work anymore. This is a major bug of Parallels.
After using the "uninstall" app of the Parallels .dmg file Spotlight works again. I rather keep Spotlight working than having Parallels RC 1 installed. BTW, the "uninstall" app does not erase some Parallels folders in the librarys or the 3 .plst files.
This topic has been covered and IIRC, the way to fix it is to not have spotlight search the folders your VM is located in.