It's not a bug, it's a feature...
The VM grabs the CD if you allow it (default). Only one of Mac OS X and any VM can access the CD at the same time.
If you don't want to have the CD mounted in the VM, just tell PD about it in the VM settings.
I thought the idea was I could move 'seamlessly' between applications on Mac or Windows in the VM - without having to shut down or decide which OS takes priority