network disconnected on unmanaged vault

I have an unmanaged vault going to a file share (\\servername\share) on my AMS server (Windows 2008). This vault contains many backups from a couple jobs and worked fine. I recently updated to the latest build of ABR11 (17437) using clean installs (ran abr_cleanup everywhere and installed fresh). Now, the agent on the server being backed up (physical server) does not authenticate against that unmanaged vault. It *does* authenticate against the storage node vaults (same userid and password) just fine.

I've attached attached screenshot and the output of the error is at the bottom of this message.

I've tried everything. I've rebooted both servers (AMS and the physical server containing the agent), I've tried creating a personal vault to a different file share on a different server from the agent, still won't work. All permissions are set correct AND the AMS can access the vault with that userid and password just fine, it's specified in the job. But everything I try, will not allow me to access that unmanaged vault, and it's a P.I.T.A.

I've uninstalled and re-installed the agent. Nope.
rebooted both server. nope
used a different file share. nope
checked all permissions. all good
accessed that same vault/share from an agent running on a different server just to test. I can do that, but can't access it from the server that NEEDS the backup.

I've seen this happen with unmanaged vaults with previous versions, but usually, one of the things I try eventually fixes it. It's very inconsistent

What kills me, is I actually tried accessing that vault from the agent on the physical server PRIOR to the backup jobs running, and it worked fine. Now it doesn't.

ERROR MESSAGE TEXT:
================
Code: 262,165(0x40015)
LineInfo: 0x9A79F20828BC7F3;

Module: disk_bundle_vs
Message: Network disconnected.

Code: 262,165(0x40015)
LineInfo: 0x9A79F20828BC7F3;

Module: disk_bundle_vs
Message: Network disconnected.

Code: 262,165(0x40015)
LineInfo: 0x9A79F20828BC7F3;

Module: disk_bundle_vs
Message: Network disconnected.

Code: 262,165(0x40015)
LineInfo: 0x9A79F20828BC7F3;

Module: disk_bundle_vs
Message: Network disconnected.

Code: 262,165(0x40015)
LineInfo: 0xBD01591C540A124B;

Module: mms_vs
Message: Network disconnected.

Code: 65,520(0xFFF0)
LineInfo: 0xBD28FDBD64EDB8E0;

Module: disk_bundle_vs
Message: No network provider accepted the given network path

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