Anyone else having this issue?
Since I upgraded to 4.2, both of my Galaxy Nexus phones can't turn bluetooth on.
I was having this issue, as were a few users on xda. There is one confirmed solution, and one that may work (only one person has had luck with it in the forums). I used the first solution.
The first solution has you using fastboot, so your bootloader would need to be unlocked. Essentially you flash a new radio, bootloader, image .. basically everything except "userdata.img" so that you can keep all your apps/settings/personalizations. And it worked for me. --- I was rooted (but with stock recovery), and I lost root. You do NOT need root to use this solution, I simply want to highlight that you would lose root if you did have it. What you do need is an unlocked bootloader, and if your bootloader is locked currently, then unlocking will cause the phone to lose all data (thus backup!, actually backup regardless!).
The second solution is if you're running CWM in recovery, you use the CWM-based update, and just reflash it (only one person in the forum tried this and it worked for him).
Link to forum:
Galaxy Nexus 4.2 Bluetooth - xda-developers