@whitgallman:
I guess you mean that you "can't" see the data on it. In that case, I disagree with your comment that it is "working fine"

IMHO this does not sound like an ecryption-related issue, since one drive letter is being recognised by Windows (unless that drive letter is really the VCD drive). Windows reporting a hard disk drive letter on this drive, should mean that the MBR is valid. If the drive was in front of me, the first thing I'd do would be to look at the MBR in a hex editor.
If the MBR looks sensible (a quick check if you're unfamiliar with the MBR, is whether that sector ends in hex 55 AA) then the problem needs further diagnosis, but is unlikely to be related to the encryption, IMHO. Depending on your skill, experience, and the value of the data, you have to decide whether to take the risks of further DIY, or to contact a DR company.
Did the drive get dropped or suffer any other unusual event, between the last time it was working, and the first time it had this problem?