I can't find anything specifically relating to ZapLoc in Facebook to remove? Could that be the problem? I can find the application itself but no options to either add/remove or allow/remove access?
I must have allowed it access previously for it to have worked, but it doesn't appear in my list of facebook apps so I can't remove its access?
I did have two apps called 'Nokia N900' in facebook which I removed, then removed ZapLoc from my N900.
I then reinstalled ZapLoc and the first time I went into the 'Set up Services' menu in ZapLoc (the menu where you tick the boxes to allow access to Gowalla, Foursquare, Facebook, Twitter) it showed all four of the services and Facebook was there and ticked. Then when I went back to the map screen to try and check in first of all I got HTTP Timeout and now I'm getting the HTTP 400 Bad request message again.
Also when I try the set up services menu again, it comes up with Gowalla and Foursquare again, but then hangs and doesn't bring up Facebook and Twitter. I have to switch to phone mode and terminate the app while it's minimised as it just hangs there at that point...

Thanks