I've had this happen, and, when I hold down the BB button to see the running tasks, there's the FaceBook app!!
It's done this a few times when I've closed out of it, but since it's designed to run in the background (Unseen) it has been popping up and taking over the system.
As soon as the Facebook App disappears from the list of running apps, the phone goes back to normal.
The thing is, its happened even when I've not been in Facebook since I last rebooted my phone!
06-11-10 12:24 PM