I often run two virtual machines simultaneously - one is Windows XP and the other is Solaris 10. Rebooting the Solaris 10 machine causes a fatal error in the Windows XP machine every time. The same does not happen the other way round.
i have the same problem with winXP and linux or 2003 server, it's pretty annoying. this is the one issue that's stopping me from buying this software. for now i'm stuck using vmware in bootcamp since it allows me to restart the VMs without crashing.