We're still investigating the issue. We were hoping to have a fix available in 3.0.2 (just released), but we are still investigating it.
In the our investigations, we've found multiple other posts regarding the XD Receiver window being stuck open in Facebook Connect applications (not just JFBConnect). We also weren't successful in getting it to work with the 3.0.0 release, which would have helped narrow it down.
Either way, we'll keep you posted to what we find.