DEC's VAX/VMS group got a customer bug report that was accompanied by a 9-track tape containing the programs and data necessary to reproduce the problem. When the engineer mounted the tape, it contained completely different data. He tried a different tape drive and this time he got the expected data. It turned out that the customer had reused the tape and recorded the reproducer at 1600 bpi on top of previous data recorded at 800 bpi. If the tape was mounted such that the drive didn't see the PE burst, it could still read the NRZI-encoded 800 bpi data. -Paul W.