Windows Server 2008 R2 and Hyper-V Problems

[Toonarmy]

Hi we have daily backups using Hyper-V, each day a different USB drive is plugged into the sever (2008 R2), Monday, Wednesday and Friday's all work OK( three separate USB disks). Tuesday's and Thursday's both fail with the same error (two different USB disks).

 

" The shadow copies of Volume \\?Volume{5eb23d37-fdd6-11e2-b9a9-e0db5513496c} were aborted during detection because a critical file could not be opened"

 

As above this error is seen with two different USB disks plugged in for the Tuesday and Thursday. Is it due to some sort of corruption within the USB disks or is this something within Hyper-V?

 

Any ideas to sort it?