I had the same experience with a Quantum Super DLT. The only way to fix it was to send it in to the company. It happened 5 times and it took me about a week to get it back. I finally had to buy a backup tape backup.
I used to buy quantum DLT machines all of the time. However, I had so many problems with the super DLT and the support was terrible. I decided never too purchase a Quantum tape drive again.