Samsung Exhibit II / Sound Is Off During Call?

I have a Samsung Exhibit II, rooted and unlocked. Since I bought it I have been having a most distressing issue:

Sometimes I try to make a phone call and the sound is completely turned off (on both ends of the call). The other side cannot hear me, and I cannot hear them. I can see the time running, the call is connected (I can see that even through the other device), but there is no sound on both ends, regardless of what is the other phone (mobile or land line).

1. No, I am not pressing mute or add call with my face.

2. It does not work at all to press speaker phone, mute, or any other button while on call.

3. No, I do not plug in headsets or headphones prior to calls, nor at any other given time. Since I got the phone about 2 months ago, I only plugged the headphones once.

4. Yes, it does take sometimes 2 or 3 reboots so that the problem goes away. But the problem does return very often. At least once a day now.

5. Restoring phone to stock did not work at all.

6. The issue is also not related to my ROM, as I already installed different ROMs (currently, I have PeachSunrise, but I am using Go Launcher Ex on top of it). I already used, with the same effect, the stock ROM, Go Launcher Ex after rooting over stock ROM, and now Go Launcher Ex on top of PeachSunrise.

7. I uninstalled all active programs (and their related services and processes, which were Lookout and Easy Battery Saver).

8. I even tried replacing some files to see if I could have the problem solved, but nothing changed at all. And, since I am not very savvy at these things, I tried replacing what I personally thought could be linked to the problem. These were:

a) phone.apk
b) contacts.apk
c) contactsprovider.apk
d) Phone_Util.apk
e) PhoneCrashNotifier.apk
f) PhoneErrService.apk
g) SpeechRecorder.apk