When connecting and disconnecting from the gdm server, you would get a lot of
messages like this in the messages file:
gdm_xdmcp_decode: Could not create XDMCP buffer!
This is because the message should be a debug statement, not a warning one.
Patch available in the upstream bug:
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.