Solution by Event Log Doctor

I started getting this error message on a Windows 2008 server, after unsuccessfully trying to type in the RDP session. While I was able to login, typing anything resulted in random behavior, as if a function key was permanently pressed.

Disconnecting and reconnecting the keyboard did not help, restarting the terminal services service(s) did not help either.

I was able to work around the issue by logging off and back on, though it will probably reappear at some point.