Image Cleanup job, error 2060029: authorization failure

Wonder if anyone is familiar with this issue.

We're running Netbackup Enterprise on 7.1.0.2 (clustered, RedHat Linux), with 2 Windows 2008 R2 media servers (servernbu01 and systemnbu01) and PureDisk 6.6.1.2 with engineering binary 20.

Recently the image cleanup jobs don't seem to be doing anything but remain active, with the following info:

10/5/2011 5:25:04 PM - begin
10/5/2011 5:25:04 PM - Info nbdelete(pid=16166) deleting expired images. Media Server: servernbu01.domain1.local Media: @aaaab    
10/5/2011 5:25:05 PM - Info bpdm(pid=5084) started           
10/5/2011 5:25:05 PM - started process bpdm (5084)
10/5/2011 5:25:05 PM - requesting resource @aaaab
10/5/2011 5:25:05 PM - granted resource MediaID=@aaaab;DiskVolume=PureDiskVolume;DiskPool=DP-PD-Site1;Path=PureDiskVolume;StorageServer=serverpdsg01.domain1.local;MediaServer=systemnbu01.domain1.local
10/5/2011 5:26:20 PM - Info bpdm(pid=5084) initial volume PureDiskVolume: Kbytes total capacity: 16773765120, used space: 13899875504, free space: 2873889616
10/5/2011 6:08:27 PM - Critical bpdm(pid=5084) image delete failed: error 2060029: authorization failure

Any help is appreciated.

Thanks!