SCENARIO
After patching a SharePoint server with normal OS patches and reboot you are no longer able to browse to the applications or Central Admin. When looking at the log you see this error from C2WTS:
“An exception occurred when trying to issue security token: Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401).”
This was on a normal SharePoint Foundation 2013 server (build 15.0.4569.1506)
PROBLEM
If you check this TechNet forum post it seems to be related to “third party monitoring tools”. Unfortunately, SCOM is considered a third party tool in this case. And as it happens, we have just upgraded to SCOM2016!
SOLUTION
According to the TechNet forum post (and this official MS post) you should update or disable any third party monitoring tool. So, uninstalling the SCOM monitoring agent, rebooting, reinstalling it with “NOAPM=1” parameter will solve the issue (atleast it did for me).
However, if that it not an option (sometimes you can’t just reboot a critical server!), disabling Load Optimization does work, even if means your SharePoint is now unsupported. So I’m posting this for all us “it needs to be fixed now and I can’t find, update or disable whatever DLL is causing this!”-techies! So setting these registry keys works:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework, create a new ‘DWORD (32-bit) Value’ named “LoaderOptimization” with a value of “1”.
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework, create a new ‘DWORD (32-bit) Value’ named “LoaderOptimization” with a value of “1”.
But as those MS people will tell you, it really isn’t a recommended solution (which is weird since it originated from MS support!).