This issue is currently under investigation
I still get this problem occasionall. Today for example I have this error once again. I always have at least one issue with backups every day since September 2012 when I went live with BE 2012. Always different and mainly backing up VMWare or Hyper-v hosts.
Trying to get to the bottom of various issues getting a single pass backup of my ESX4.1 VMs working.
Appiled the hotfixes to clear the hanging GRT job error but now get verify failures saying the the vmdk disks are corrupt.
The verify job lasts about 20 seconds at best.