This usually happen when you try to refresh the library in the SCVMM. This occured due to VMs that are currently accessing library vhd files/iso. Due to this you are unable to perform refreshes on them because hyper-v has a lock on them. Make sure no Hyper V host is accessing the library share folder, no activity (example: copying/access to share folder) and no mountig of CD to VM.
Once you have stop the above activities, you should be able to refresh the library shares.
