I wrote an article back in November last year about disabling Secure Negotiate on Windows 8 clients and Windows 2012 Servers when using third-party storage that doesn’t support this mechanism.
If you’ve implement the RequireSecureNegotiate registry key to your servers, you may find that you are unable to access shares on these servers and getting errors such as “Access is denied” or “The specified network name is no longer available.”
Chances are, you need to ensure that this key has been set on all 2008/2012 machines in your environment to ensure that they are all communicating the same way.