According to reports on the Parallels user forums, Parallels 5.0.x has problems running Kaspersky Anti-Virus on some of Apple’s newly released iMacs and Mac pros with Nehalem-based Intel processors, where random applications crash (XYZ as encountered a problem and needs to close).  This is not affecting older Mac models, and Parallels is working on a fix.  A workaround has been posted to http://kb.parallels.com/7077