The notification is basically pointless, so you might as well even disable it. This is because of a recent change to the way the ladder works. There is nothing wrong with your installation.
The development team is working on fixing some of the problems with the new system. In the meantime, all I can say is: keep searching and eventually you will get a match. I guess you can surf the web or something while you wait. After you get a few games in, you should find matches more quickly.
Also, if you just want to play 1v1 and don't care about whether it is an official ladder game, you can host your own custom 1v1 game.
Here is a discussion about it:
viewtopic.php?f=2&t=18083&start=37The devs say they are working on a fix for this. The fix won't mean we get games instantly, but it should mean that people don't have to wait ridiculous amounts of time for a game, assuming there is at least one person out there who can play against you.