HP Colorado Backup Tape Error

[thearbers]

I am using an external HP Colorado Backup II 8GBe Travan tape drive. Recently
it will only run for about 20 minutes. After 20 minutes it appears hung up and
stalled. It will remain stalled for about 10 minutes and then report
"An error occurred while writing the backup data.
A defective or damaged area was detected on the media.
...
(08-03-23-01-1191)"

I have tried using a new tape cartridge and it makes no difference. I tried
backing up different directories and if it finishes in 20 minutes then there are
no problems. If the Backup is in the verify stage after 20 minutes then it
reports an error reading from the tape, instead of writing. At the 20 minute
point the backup has processed 402,422,852 bytes in my latest attempt.
Any advice would be greatly appreciated!