There's a whole thread already dedicated to this issue, and the new version of JFBConnect (v2.0) should fix this. There's a reason it was called a Release Candidate. We're not guaranteeing there's no bugs remaining now that we've removed that title, but we've been very proactive in getting 4 releases over the last month out to fix issues that people have been encountering.
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I'll try to get to your JFBInvite questions today, but they haven't been the highest priority, since we've been working on the fatal error you mentioned below and also have to spend extra time reading additional posts relating to issues that have already been reported (and even resolved by the time you posted this).