I’m using WordPress 3.5.2 on two of my blogs. One of them had an existing gallery I simply updated. This ended up with the error described by @gsfergusson (but could be reactivated by @mweichert’s advised guidance of downgrading!). The other blog is a freshly started one without an already existing gallery. I’ve just been taking a look at the plugin’s options and it seemed to be well working. I’ll be adding a few pictures soon to check out the further behaviour by creating a new gallery.
I’ll let you know what happened if you like.