WordPress MU

Hi.
I used some plugin and accidentally migrated page template settings/options to all blogs on a wpmu site I'm developing.
The result is that the usual drop-down menu in the page edit screen is gone, so I can't select template for existing or new pages.

Any ideas on how to get it back?

Reselecting the theme usually brings it back.

You're right as always. Excellent, thanks Andrea. :)