I have a SureStore DLT 80 with the same issue. Moved it to the storage room for 6 months, then had to use it again. Worked fine until last Thurday (10-19-06). Worked great for about a month. Then the same thing happened (all left side lights are on)and device is shown off line in Backup Exec. v8.6. The software is to old and is not supported anymore, and the tape drive is in the same boat. Looked at the internet, and can't find anything. HP website didn't help either. I'm assuming it's toast. Don't have the time to mess with it.
Sorry I couldn't be anymore help, but at least you know that you ain't the only person that has this issue. If anyone knows what's going on, please let us know.