Dear Tim, I agree with JoaoMatos that this appears to be a hardware issue. A reboot might fix it. If you have a utility like HP Storageworks you might test out your tape drive there. You might need to re-apply the driver to your tape drive with the backupexec wizard.
Sorry for my late response, I've called the company where i bought my back-upunit, They sended a guy who looked at my unit. He said there was an update with service pack 4 or something. Yes i have reboot my server. Didn't updated the service pack tho. But another guy will check for the hardware first... Cause i don't really trust it. Thanks for the responses, I'll keep you up to date