Thank you for the suggestion. I was not able to find anything that addressed this particupar issue. The drive is accessible and the non- encrypted / vault parts are working fine. The issue is the dialogue box that comes up, only allows a response of “OK” and then closes without any opportunity to enter a password for the vaulted portions of the drive.
*** Additional Information: I have two of these drives. When i use drive 1 by itself, i get the error message I described and no access to the vaulted parts of the drive. When I use Drive 2 - i have no issues at all, the drive behaves as expected. When i put BOTH drives in, drive 1 not behaves normally and I can access the vaulted section of the drive, even if I have done nothing else with Drive 2 - it is simply present. It would appear that somehow Drive 1 has now associated itself with Drive 2.
I will now attempt to backup Drive 1 while both are attached.