Thanks in advance for your help. I will describe my situation and my problem here:
1. Create a backup job for my Windows server 2008 R2 server (Hyper-v host with 2 guest vms). Backup Exec is running on the host and the backup includes both VMs. I've set the data retention period to 12 hours.
2. Run the backup, which uses up about 290Gb of a 320 GB drive. The backup completes successfully.
3. The next day, run the backup again to the same drive. Note that more than 12 hours have passed and if I navigate to "backup sets" the expiration date and time for the previous backup shows to be in the past.
4. Note that the backup runs for ~30GB, enough to fillthe remaining space on that USB drive. Then, the status changes to "loading media" and the backup hangs there indefinitely.
I'm not sure why it does not overwrite the previous backup data since the retention policy has passed. please note that under Backup Exec stabbings, I have set the "media overwrite protection level" to "None". I'm not entirely sure what that does but it does not help this particular situation.
Thanks!