Windows backup on Server '12 HyperV parent returns error when backing up host component

We have a Windows Server '12 HyperV parent that is running bare metal Windows Backups of itself and of its HyperV children.  The backups complete successfully except that they fail to backup the Host Component.  The exact error message is:
Error in backup of C:\\ProgramData\\Microsoft\ during enumerate: Error [0x8007007b] The filename, directory name, or volume label syntax is incorrect.
Application backup
Writer Id: {66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}
   Component: Host Component
   Caption     : Host Component
   Logical Path:
   Error           : 8078010D
   Error Message   : Enumeration of the files failed.
   Detailed Error  : 8007007B
   Detailed Error Message : (null)


Backups are being performed to a local USB drive.  All other components (bare metal, VHDs, etc) backup successfully.

Several months ago, I did a restore of a child's VHD to an "alternate location" so I could recover some files out of it.  If I recall correctly, something broke as a result.  I don't remember if the subsequent problem was that the VMs wouldn't restart properly or if they wouldn't back up.  I remember that some file location had been altered as a result of me backing up to an alternate location, and that I had to correct a registry entry to fix the problem.

I suspect that the current problem backing up the Host Component is somehow tied to whatever fix I had to do several months ago.  Unfortunately, I didn't document the problem or the solution, so I don't recall specifically what I did.  I do recall that whatever I did fixed the immediate problem.  Searching Google for assistance (even specifying experts-exchange.com) has proved fruitless.
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SINC_dmackAsked:
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KenConnect With a Mentor COO/Senior Systems AnalystCommented:
This may seem a silly question, but why do you have two backslashes before and after ProgramData in the path name? Is that the exact error? You may have entered this info incorrectly the first time around and that is why you had the failed backup previously.
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SINC_dmackConnect With a Mentor Author Commented:
Ken, not a silly question--yes, that's the exact error message.  I fired up REGEDIT, and apparently the last time I opened it was when I made the change to fix whatever the problem was several months ago.  

The key is:
HKLM -> Software -> Microsoft -> Windows NT -> CurrentVersion -> Virtualization -> StoreLocation

The value is:
msxml://C:\\ProgramData\\Microsoft\\Windows\\Hyper-V\\InitialStore.xml

I think when I did the restore, that entry was changed to whatever folder I restored the VHD to.  I'm confident that the updated entry was made as a recommendation of whatever website I found the fix on.

I checked the same key on one of my other HyperV '12 Servers and its value is:
msxml://C:\ProgramData\Microsoft\Virtual Machine Manager\HyperVAuthStore.xml

All I can think is that the website where I found the fix had the wrong syntax, because there's no reason I would have consciously implemented extra slashes.  This is probably a case of me just taking at face value the purported fix and copy-and-pasting it into my affected server without questioning the syntax.  

So it seems pretty apparent that the server having the problem may have the wrong registry entry. I've copied the entry from the healthy server to the one experiencing the backup issues and will report tomorrow if this has fixed it.  Thanks!
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SINC_dmackConnect With a Mentor Author Commented:
So, I rebooted the HyperV parent after changing the key to:
msxml://C:\ProgramData\Microsoft\Virtual Machine Manager\HyperVAuthStore.xml

The HyperV service wouldn't start.  Good thing I copied-and-pasted the original entry here.  I modified the key as follows and rebooted:
msxml://C:\ProgramData\Microsoft\Virtual Machine Manager\InitialStore.xml

The HyperV service wouldn't start again, so I reverted to the original key and rebooted:
msxml://C:\\ProgramData\\Microsoft\\Windows\\Hyper-V\\InitialStore.xml

The HyperV service started and all of the children became available.  

So, I went back and just took the extra slashes out of the key, after realizing that the healthy server had not only a different XML file, but that it was stored in a different location.  One more reboot, and everything came up properly, with the correct number of slashes in the registry key.  We'll see how the backup goes tonight.
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KenCOO/Senior Systems AnalystCommented:
Sounds good. Yes, I try to backup any registry hives before making changes. I will check back to see how it went.
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SINC_dmackAuthor Commented:
Last night's backup completed successfully.  

I Googled for "msxml://C:\\ProgramData\\Microsoft\\Windows\\Hyper-V\\InitialStore.xml" and found this site, which does include a fix with that exact syntax: http://zoomcloud.blogspot.com/2013/04/hyper-v-error-15500.html

I don't know if this was the specific site that I found several months ago when experiencing my initial problem after a restoring a VHD to an alternate location, but I feel at least a little better knowing that it's at least possible since there is at least one site with the fix with double slashes.  Thanks for your help, Ken!
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KenCOO/Senior Systems AnalystCommented:
Glad you worked through it and thanks for posting your solution. Many times a simple comment makes you look at something a little different to find the right path. Might not even be the solution but gets you going. Take care.
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SINC_dmackAuthor Commented:
Ken's comment pointed me towards something that probably should have been apparent to me in the first place, and fortunately regedit on the affected server opened to the exact key that was causing the problem, making troubleshooting a lot simpler.
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