I ran into an issue with some Citrix servers in the environment. Users were getting a protocol driver error. After poking around I noticed ICA was not listening on port 1494. It appears that this issue was caused by Microsoft patch MS12-024. Known issues with this security update After you install this security update on a Windows Server 2003 SP2-based terminal server, Remote Desktop Protocol (RDP) clients or Independent Computing Architecture (ICA) clients may be unable to connect to the terminal server.