I have had many friends report that they cannot use linphone on their Samsung Note 2 (and 3 also) because when a call is started, the call window goes all black and therefore one cannot hangup the call and do all the normal UI stuff.
At first I thought it was user error but I have confirmed this behavior, which seems to be specific to Samsung Notes. I have an S3 and linphone works fine with it.
In fact, even with the Notes, the call does go through even though the screen is all black, which leads me to suspect this is merely some incompatibility with some Samsung firmware specific to the Note family only.
Anyway, since I don't own one I cannot debug and grab the logs, but since this has now happened on 3 or 4 Notes I'm pretty sure it's a legitimate bug that needs to be fixed.