I'm receiving this error message when opening .qxd document or opening Quarkxpresss 6.5. Also when I am opening Quarkxpress 6.5, I see the splash page for 6.1, then I receive error message.
You could try to delete the pref file, but if you can re-install, that's probably the way to go. It sounds like something inside the program got messed up. You could also try repairing permissions, but that will probably not solve this either.