Gallery Javascript POST Error

I’m running Radiant 0.8 (gem) and Gallery 0.7.14 extension.

I can’t edit, delete, or move my gallery items on the Gallery admin

If I look at the Console in Firebug (a web developer extension for
Firefox), I can see that the javascript POST calls are getting “422
Unprocessable Entity”. What could be causing this? I have run the
migrate and update scripts on Gallery just to make sure, but those
didn’t fix it.