Hello guys
I had the same problem, I updated all my sites to 3.3.1 and they all worked perfectly except for one. They all run with custom themes so I chekcked that along with all the plugins on the site that wasn’t working but nothing changed.
I eventually checked the permissions and found that the wp-includes directory was set to 750 and when I changed it back to 755 it worked perfectly.
I hope this helps somebody.
