Nicholas - Utilizing a utility such as tapeutil's rwtest function, exercise the supposedly bad tape to evaluate whether it really is, or if just one drive is acting up. I would additionally physically inspect the tape, pulling out a meter or so of it to have a look: in some cases, a drive has a mechanical defect and is chewing up tapes - where it will mangle all your tapes if given the opportunity. (In 3590 experience, I had a case where the CE extricated a "bad tape" from the drive and left it for me - where the tape's leader block was missing... which begs the question of where it was: still inside the drive, causing mayhem with other inserted tapes.)
Richard
