I have a DLT 8000 (40/80 GB) which does some peculiar things.
When I switch it on with a tape in it I get an a light display or "error-message" (up to 8 double-flash lights of all indicators down the left-hand side of the unit after which the unit returns to normal function) however the interesting thing is that this ONLY ever occurs when a tape is write-protected (indeed ALWAYS when the tape is write-protected). The behaviour is identical regardless of whether the tapes are Win2K/NT or Legato backup format and regardless of whether they are being tested independently or attached to a server.
I acquired a second DLT 8000 drive and tested that.
The "error message" occurs on both units only when tapes are write-protected and never when I they are not. There are no other signs of error on either unit and both drives, whilst second-user, were replaced due to upgrade to Super DLT not because of head wear.
Additionally I have performed a small backup sets on tapes that apparently caused the error after allowing them to load write-protected (generating the "error message") and unlocking the write-protect tab. No issues were encountered.
Can anyone shed any light on this?