First off, do you have an SMDI integration to your CallManager? If so this is a problem, if not, I would recommend disabling the Cisco Messaging interface. If you do, ensure your serial port is working properly from a Windows standpoint. FOr example, connect the serial port to a router, can you use hyperterminal correctly. This is from the CallManager 3.3.3 Error Message link
Error Message
%CCM_SUMI-CMI-2-kSerialPortOpenningError: Error when CMI tries to open the Windows NT serial port. Serial Port Openning Error [String]
Explanation When CMI tries to open the serial port, Windows NT returns an error.
Recommended Action Make sure the serial port is available.