Invalid signature errors are thrown in the "system log" and "work manager" log when connecting to a share on a SAN, or MAP will not validate paths (see screenshot below) found on a share that you can connect to without issue in Windows Explorer.
This could mean that there is an incompatiblity with the NAS and/or SAN and the Server 2012 security model.
Accessdata Products using MAP (e.g. AD Ediscovery, Summation Pro).