We run an NTBackup job on a Windows Server 2003 R2 SP2 with all updates (as of Q4-2011). It works well backing up two WS2k3 servers as well as the backup server itself. However, we have been unable to successfully back up our Windows Server 2008 R2 machine ("G5-01"). It often runs for about 2GB worth of backup and then dies out with one of the below error messages. It should be more like 20GB for the full server. We have tried using the admin share (C$), an explicitly shared drive share, UNC and mapped drives. The result is the same each time, the only thing that varies is the amount of stuff backed up before it chokes. We've also run NTBbackup from the UI interface, from the command line and as a scheduled task. We are backing up to 400/800GB tapes and they have plenty of space available on them (blank media).

Error: \\G5-01\c is not a valid drive, or you do not have access.

Error: \\G5-01\c$ is not a valid drive, or you do not have access.

Error: Y: is not a valid drive, or you do not have access.

Error: Could not access or create backup catalog files. Verify that you have full access to the working folder and there is disk space available.

The job is run as Administrator and we have no problems logging onto the server and transferring files. The Event Log on the WS2k8 is not much help, as it has success audits for each login.

All of the hardware involved (HP DL360 G3, HP LTO Ultrium 3, Adaptec 39320A) has the latest supported drivers.

We've seemingly tried a bunch of different options but are wondering where to look next to resolve the backup issue. We've been super happy with our reliable schedule task for years but this one is stumping us!