Well, I checked the integrity, and it was ok. So I made a backup, uninstalled all the files. And tried to play it.
It still doesn't work.
 

Some time in December I backed up my files for Super Meat boy and didn't play it until recently. Whenever I try to load it, Steam will say "Preparing to launch Super Meat Boy..." as normal, but it won't load. A minute later a message will come up saying Super Meat boy can't connect to the Steam Cloud. I have the option to run it without the cloud, but it still won't load. The next time I tried to open SMB, it prepared to launch, and the Preparing to launch window disappeared, and the game never loaded. I restored the backups, but the same thing happens. Is there any way I can fix it?
(BTW, Braid, TF2, and all my other steam games work perfectly fine)