The other night I had my Veeam box decide it was not going to backup my VM’s.  This, naturally, is unacceptable behavior!  The error I was getting was the following (I cut out all the junk from my environment):

Processing <VMName> Error: An unexpected network error occurred. Failed to write data to the file <StorageUNC>.vbk]. Failed to download disk. Shared memory connection was closed. Failed to upload disk. Agent failed to process method {DataTransfer.SyncDisk}.

Before you jump to the obvious, there were no network related issues.  I did some digging and I found the solution!  I apologize to the random blog that I found the solution from, I have since closed the tab and lost the link.  Anywho, the following directory needs to be empty:

C:\Windows\TEMP\vmware-SYSTEM

I had a log file left in the directory.  Cleared it out, bounced the box (because why not?), and kicked off a backup of all my VM’s which completed without issue.