After rooting my Samsung Galaxy Note 2 and switching to CyanogenMod CM10.1, I’m randomly having issues with in-call sound problems, specially when upgrading to a new nightly build. Sometimes after an upgrade, the speaker on the phone is mute when making calls. That means I can’t hear the ring tone or the person on the other end of the line.
Googling for the solution, I found this thread in XDA developers. Turns out a potential solution consists of turning on the screen lock sound and rebooting. I have used this trick once and it worked. Amazing!