Facebook Connect SSO not working on some iPhones

I have implemented FBConnect SSO in my iphone application according to this tutorial. I have tested it on two phones so far, one of which lets me use the function just fine, whereas the other phone simply opens up the Facebook app and closes it right away. I am able to establish a valid session, yet the dialog seems to just close on me on one of the ones.
What could be the problem? Any help is much appreciated.