Parallels 5 doesn't start – no error message

hi,

i bought parallels 5 the other day with the macupdate spring bundle.
the installation went fine and i entered my licensing information. but then, parallels quit without any message or error (the little bright dot in the dock just disappeared).
now whenever i try to launch it, the icon bounces for a few seconds, the dvd-drive goes into ready-mode and then it quits – again without any error message.
i tried re-installing the software a couple of times which did not help. in another thread i read about the parallels services (prl_disp_service and prl_naptd). both of them seem to be running just fine.

and i'd be thankful for any help