hi bradholland, i’ve done a facebook app inside a iframe, and i’ve a similar problem.
the cause is the fact that fb doesn’t accept an url coming outside the app base domain: for example if your app is located at https://apps.facebook.com/xxxxxx/
you can access any sub directory under xxxxxx/ level but not file of the same level. (the wp root in our case)
i tried to resolve the problem setting target=”_parent” or even “_top” but this last is a pure redirect at the app domain.
SOMEONE ELSE CAN HELP US TO ACCESS WP-LOGIN.PHP INSIDE FACEBOOK CANVAS ?