Grant Extended Permissions Error from FB API

ClvrTv
El Presidente
Friendly Neighbour

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WP 3.1.2
Ultimate FB 1.0.9
Network install, all sub sites using the master API key / IDs / etc
Domain Mapping Plugin

I can't remember if this is the first time I've tried to Grant Extended Permissions on a domain mapped site, but when I do I get this error in the FB pop-up that usually has the Allow button:

API Error Code: 191
API Error Description: The specified URL is not owned by the application
Error Message: redirect_uri is not owned by the application.