Issue with Proximity Sensor during calls

Apple won't sort this any time soon.
They'll do it on their own sweet time.

They're a bag of **** for listening to customers/fixing issues quickly nowadays...

Count me in also,same issue.Very disappointed so far

Also having this same issue, managed to search my addressbook, put someone on hold and attempt some FaceTime action.

Hope this isn't a hardware issue :'(

The only temp fix i can see is to press the home button and therefor you are unable to mute/hold from the home screen...

Then we will randomly launch other apps. Someone needs to write an app that does nothing but provide a blank screen so we'd at least have to push the home button to damage our call.

Having the same problem...hopefully fix is in the works

FYI - I just spent 20 minutes experimenting with a call to my landline. I pressed the home screen button so I wouldn't make any unwanted calls in the process. What I found concerns me even more now. I held the iPhone up to my ear, making good contact, so as to trigger the proximity switch. I braced my elbow on the desk to keep the iPhone perfectly still for the next 20 minutes. During that 20 minutes the screen activated 37 times at random intervals. It would remain blank for up about 6 minutes at one stretch and then began to rapidly flash on and off about 6 times then go back to being inactive for another 2 or 3 minutes. All of this with the iPhone held completely still in direct contact with my ear. I tried resetting last night. I even went so far to restore it as a new iPhone. There is no case on it. I'm running version 4.0 (8A293) with model # MC319LL. It almost seemed like something was interfering with the sensor either electrically or thru the software.

66sweep's experience lines up with my own. I was sitting in my bed last night paying very close attention to where the phone was because I've been following this issue. Without moving my phone and with the sensor (directly above the speaker) flat against my head, the screen was randomly turning on and off. If you get a SMS or some other popup notification while you're talking on the phone, it almost seems to get worse. It's almost guaranteed you're going to tap 'view' with your face so then you're face texting or whatever else. I sure hope this is fixed soon. It makes me look like a massive jerk when I hang up on people during work calls or when I hang up 5 times on my fiance in one night.

PROXIMITY DETECTOR: I am experiencing constant problems with the proximity detector causing various problems after few minutes into a call i.e.: cheek dialing, muting, launching face to face, and ending calls.
ANTENNA (POOR & VARYING SIGNAL STRENGTH: I am an amateur radio operator (extra class) and was very interested to see how Apple engineers could place an external antenna in the grip of a user while overcoming the elementary problem that touching the antenna will cause a change in impedance (and therefore its resonant frequency) to change ... which in turn will cause a mismatch (high SWR) and a malfunctioning antenna.
The answer was obvious when I received my 2 iPhone 4s - apparently Apple did nothing to overcome this easily predictable problem ... other than offering a $29 "bumber".
Come on Apple, I am a long time supporter and stock holder I know you can do better than this!?

I have had all the issues raised in this thread, and have tried some of the suggestions (thank you!) mentioned by some, and the reset did seem to help with the proximity problems. But I would like to point out that when I temporarily was using an older leather case for the phone, it seemed to still revert to some of the symptoms as before, but when I put the phone into a silicone type case, I get no more issues with muted calls, hang-ups, or random dialing. So in my not so scientific research, I've found my fix.

I just got off the phone after talking with Apple Technical Support. The Level 1 rep said they had nothing listed in their system indicating this is a known problem, at this point. This means there is no scripted trouble shooting steps or solutions beyond what's already been discussed here. He elevated it to a Level 2 Tech. It appears the only help Level 2 could offer was to exchange the iPhone for me. Unfortunately, the none of the 4 exchange options will work for me right now. The options were: 1 & 2 involved being without a phone for up to two weeks or paying for the use of a loaner. #3 Send me a new one and send my old one back upon receipt of the new one. The issue here was a $700 hold placed on my bank account until Apple receives the old one. Understandable, but just won't work for me. #4 Go to an Apple store. Nearest for me is 150 miles. So, I guess I'll use a headset for a week or so until there's either a software update or I can make it to an Apple store. In the interim, I would HIGHLY ENCOURAGE each of you that is experiencing this issue to PLEASE CALL APPLE so they can better document the issue and possibly speed up their response.

Also having problems with the proximity sensor. I was occasionally able to activate key strokes even though the sensor was pressed firmly against my head and the display appeared to be off at the time.

I'm confident that Apple will come up with a solution for this - the iPhone 4 is an amazing product, and in spite of this problem I can't think of another device I'd rather own.

@skls: I agree that Apple will fix it, if it can be done through a software update, but as far as Apple support is concerned there is no wide spread issue that's been reported to them. I can't stress enough how important it is for everyone to give Apple a call and open a case number.

Yes, you're right and I will give them a call. I forgot to mention that I also tried the reset fix, but it didn't work for me.

I am having this exact same problem. I have had an iPhone since 2007 and never once face dialed in three years. Since I received the phone on wednesday, I have been face-dialing and hanging up on calls left and right. It is infuriating. There needs to be a fix for this ASAP.