You failed to provide a valid list of administators. You need to supply the administors using either a "fb:app_id" meta tag, or using a "fb:admins" meta tag to specify a comma-delimited list of Facebook users.?
This is something that Facebook appears to have broken on the Tuesday code push. I'm trying to get it sorted with them now, as the Like button is not supposed to require fb:admins or fb:app_id to be defined as far as I can tell. It certainly didn't until this week.
Facebook claim that it was always intended to work like this, and that pages can only participate in the Open Graph if there is a defined application or list of administrators, so that OG nodes have controlling parties.
The fact remains that it worked without those requirements before though...
Anyway, I've worked around it. If you don't define an application or administrator user IDs, I don't include Open Graph tags any more.