Execution permission cannot be acquired
Execution permission cannot be acquired.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
System.Security.Policy.PolicyException: Required permissions cannot be acquired.
at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Boolean checkExecutionPermission)
at System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Int32& securitySpecialFlags, Boolean checkExecutionPermission)
Root cause and how to resolve
The error is that there is an assembly is trying to load which has an assembly level RequestMinimum security set specified. The CLR security policy was not going to grant that assembly what it had asked for in its minimum grant set, so the assembly was not loaded and that exception was thrown.
You’ll need to find which assembly is failing to load, It might be an orphan dll when you retract a farm solution or third party solution in your farm, then delete it (or move it over to another location for backup)
In this case, I think there is a dll that related to Ajax is stored in BIN folder of Admin Central virtual directory, such as C:inetpubwwwrootwssVirtualDirectories25108bin. You could take a look at this location and delete it.