Help resolving a failing backupexec backup.

I have a customer who's backups have been failing a lot of late. They have been running fine for many years but now we seem to be having issues.

I have managed to run a successful backup in the last few days but it failed again last night. This time it is asking for overwrittable media. I thought I had removed the overwrite protection but it seems I haven't. As you can probably tell I am no backup expert.

It is a simple set up with one SBS2003 server a Dell R1000 removable disk drive with 3 available disks that rotate every three days.

I just need an experienced Symantec Backup Exec user to help me for an hour. They are using Backup Exec 11d.

I will remote into the server and I then invite your as a guest so we can work on the issue together and maybe on the phone too. You do not require any software to access the server.

I need this looking at today, starting immediately.