I have the very latest nightly build of CyanogenMod 12 (March 21st, 2015) installed on a Nexus 4. For about a month I haven't been able to connect my phone to my computer. I have the latest USB/ADB driver installed.
When I go into the "Developer options" to toggle the "Android debugging" option, my phone automatically reboots. It appears to just do a soft reboot. Also, after it reboots the "Android debugging" option hasn't been changed. (It remains enabled) It also reboots when I turn off "Developer options" but it actually successfully has disabled them after it reboots.
If I go into the "Storage" settings, click the menu in the top right, then "USB computer connection, it doesn't actually open up the computer connection options. Instead it just causes the page to recalculate the storage percentages, like it refreshed the page or something.
I've been thinking about backing up my phone and reflashing and reinstalling everything to see if that fixes it, but how am I suppose to back up my phone if I can't copy the backup to my computer so it's safe for when I format the phone?
Anyone have any suggestions on how to go about fixing this?