DeeDee,
The requirement to encrypt or lock is indeed set by a policy in an environment managed by PGP Universal/Symantec Encryption Management Server. If you chose to lock, it should allow read-only access.
If you are unable to access the drive after removing it, even from the same system where you had it locked as read-only, it should not be related to PGP specifically. We would control the data flow to and from the device, but nothing more. Nothing about the drive itself or its contents should be mosified by our software.
Did you remove the device according to the Windows standards (i.e. the Safely Remove Hardware option in the system tray)? It sounds more like an error due to Windows not shutting the session down properly to maintain the data integrity of the drive.
Does Windows recognize the device at all when it is plugged in, or does it not give you any sort of prompt at all? Is the device listed if you go into disk management (click the start button, in the search bar type Disk Management and hit Enter)?