ESXi 5.1.0 1065491 - one VM hangs for over an hour at "clone: 21%" during backup

4 VMs on this host, the other 3 all backup without issue.  Backing up over GigE to external iSCSI NAS.  Log shows no errors.

http://pastebin.com/QSsdAuLa

Watching the console when this backup runs, it smokes through the 1.vmdk file quickly, This file is 73Gigs.

Then the 0.vmdk file clone starts and it just hangs at 21% for over an hour.  During this time there are no errors, and the NAS reports there is no activity on the SAN interface.

I noticed one particularly weird behavior on this VM during the backup process (it is a Linux VM) - the time gets out of sync by about 4-5 minutes when the clone stalls at 21%, then it gets back in sync when the process completes.