For several days after an Exchange 2010 on Windows Server 2012 install, I ran into this error message, when accessing anything in the Exchange Control Panel (Options) via Outlook Web App:
After numerous web searches, covering everything from Default Website bindings to ECP authentication schemes, I stumbled upon something odd when I opened "IIS Services Manager":
Under "Application Pools", I double clicked "MSExchangeOWAAppPool" and found a ".NET Framework Version" of ".NET Framework v2.0.50727".
I returned to "Application Pools". Next I double clicked "MSExchangeECPAppPool" and found a ".NET Framework Version" of ".NET Framework v4.0.30319".
The two did not match. Furthermore, Outlook Web App was NOT causing me problems.
After setting "MSExchangeECPAppPool" to ".NET Framework v2.0.50727" which matched the setting for "MSExchangeOWAAppPool" my problems were resolved.