We've got an MSL6060 with 4 tape drives, and had the same issue on a number of occassions. Each time with Tape Drive #1 (slot 2). Pulled the tape drive out, and we have not had this issue again, although I need to install it again sometime.
I suspect it's got to do with that drive you've replaced. Could be newer firmware that's causing the issue.
Start with:
1. Reinstalling the drivers for the drives through BE. Restart the services, and try again.
2. Delete any entries for your old drive you've replaced.
3. Update the firmware for your MSL6060 using either HP Library and Tape Tools or the MSL web front-end itself.