Having said that (see above correspondence with diamondcard), this morning Twinkle started hanging up on incoming calls after only a few seconds. I had had this problem with linphone a few months back.
Anyway, frustrated, I closed Twinkle and then deleted linphone on my system (pretty sure this was 3.6.1 from sourceforge). I reinstalled linphone 3.6.0 from the VL testing repository and it has been working flawlessly all morning. I loaded openvpn first, but doubt that makes any difference. Your linphone has not hung up on any incoming calls, so far at least. I will use it exclusively now and let you know of any problems. I am home today and AT&T is my internet service. I have a faster cable service (charter) at the office and we will see how that goes tomorrow. I have not yet tried the conference phone gadget on linphone but will no doubt soon. I am really pleased.