Read all about the ladder matchmaking algorithm here:
http://wiki.warlight.net/index.php/How_Ladder_Games_are_Created
and the announcement with the changes here:
http://blog.warlight.net/index.php/2011/05/announcing-warlight-1-4/
Basically, you don't get any games because you have played most people in your range too often already and the algorithm waits for a player to be available that you haven't played often yet (during the 3 months that count).