Behind the Scenes > Facebook Applications > Click Here to Disable (under Facebook for Fan Pages)
If that doesn't work, or to just make sure it's unlinked, head over to your first Facebook page (the one you want to unlink). Once you go into your settings, you'll see a list on the left. Click on "Apps". If you see Fine Art America listed here, remove it by clicking on the 'x' or by clicking on Edit Settings > Remove.
Come back to FAA and go Behind the Scenes > Facebook Applications. Relink to your new page.
