I am getting this coreTelephony error and a whole lot of the other trouble after updating to 10.11.1.
My system is a 2013 Mac Pro with the home folder located on a second SSD connect via Thunderbolt, and that seems to be the problem.
I have been running with developer's preview of El Capitan since it was first released. Previous updates did not cause any problem. Only this one.
Symptoms:
1. The coreTelephony error dialog
2. All settings are gone. All of them, and I cannot set any preferences. The system cannot remember any setting change: e.g., I can go into the settings for the trackpad, change a couple of things, exit, then go back in immediately and the changes are not there.
Other people posting here mentioned that having the home folder on a separate drive might have something to do with this problem, and it does, I think. And here is why. Simply going into the User and Groups pane of system settings and pointing to the home folder on the external drive does NOT fix the problem. However, if I copy my home folder back to the boot drive (SSD) and point to that, all is well. It simply will not accept having the home folder on that external drive (a Samsung SSD). Someone suggested that you had to have another admin account of the boot drive for this to work, but I did that and it did not help.
What is really strange is that even doing a restore of the system from a Super Duper backup from prior to the 10.11.1 update does not fix the problem.
So I am up and running, but I don't want my home folder taking up space on my boot drive. I will keep experimenting and report back if I find a solution.