Originally posted by tawnyowlLooking at your stats - your timeout win when your rating dropped was whilst your rating was still provisional. The FAQ under the help menu will explain this further, however now you have a non provisional rating it will not happen again...
Why does my rating drop, when I claim a timeout win?
The rating calculation (see below) means that until you complete 20 games (i.e. while you still have a provisional rating), it is possible for your rating to go down even when you win a game.
The games you claimed timeouts in were within your first 20 games and therefore can result in the loss of rating points.