Just a heads up for Trackmania United players, Nadeo's main player logon server is currently down. This ONLY affects the United accounts, all the free TM Nations accounts seem to be just fine.
Hopefully this problem will be fixed in time for the 'Race Of Champions' time slot later today. I shall edit this post once things are working again.
Just spreading the word that it's not the user's machine at fault! EDIT: The problem is now fixed but please allow time for the TMUF servers to re-appear!