Parallels 5 Causing OS X Corruption

I upgraded from Parallels 4 to 5. My guest OS is Windows XP. Twice since my upgrade to 5, OS X has been corrupted while 5 has been running. After the second crash I upgraded OS X to Snow Leopard as a way to recover the OS. Yet I'm still having problem. When I start Parallels it still crashes OS X.

I don't want to start Parallels again until I know what might be causing this problem. Any ideas?

-J