Just in, from Bashiok in the Blizzard Forums:
Due to an issue with the Grandmaster league we’ve temporarily locked league reassignments. This means that all ranked games are correctly awarding (and subtracting) points, all changes to player’s internal matchmaking rating continue to be made, but the ability to be promoted/demoted to a different league is temporarily on-hold. When this lock is released, the next win will process the correct standing and any league reassignments will be carried out as they would have.
We currently have a hotfix for the Grandmaster issue in testing, and expect it to be implemented very soon. Once the fix is in and verified the lock will be removed and league standings will continue as normal. We’ll make another announcement at that time.
It’s important to note, again, that your games played now continue to count toward your standing and a possible league reassignment.
I guess someone screwed the GM leagues badly. Let’s wait and see.