Nancy - A Flush operation refers to writing to tape all the data which the tape drive has buffered...a sync operation. Sounds like you have a drive problem. But I've experienced what seem to be drive problems when the actual problem was a cable or SCSI terminator. (We had what looked like a drive problem for about a year: switching the terminator caused the problem to go away. Lesson: never overlook trivial causes.)
Richard Sims