Media Bay In Cubase 5 Hangs.

Hi there. Wondering if anyone can help please. I Updated Cubase 5, version 5.0.1 to 5.5.0, then to 5.5.3. Every thing works fine, except when I open up Media Bay and try to click on Tabs or Files. Every thing locks up and hangs and I have to :Control/Alt/Delete:Task Manager to shut down Cubase every time. Sound And Loop Browser are okay, but not Media Bay.
If anyone has come across this problem could you advise please thank you. I use windows XP Professional-service pack 3, Intel i5 processor. Thanks.