I'm having the same problem - well this and a couple of other problems, but let's not go there right now.
As for the proximity sensor, I have put people on mute, dropped calls, dialed numbers (and the associated beeps) while on the phone with someone, I even had an instance where my cheek selected "Contacts", then a contact, then ringtone and then actually played the ringtone, all while I was on a call.
Very frustrating. Looking forward to a fix...