I hope this helps some of you folks who are having issues on the S3 and S4.

We found issues with the S3 and S4 API specifically when using the AudioManager's functions like:
Vibrate, Alarm and putting the phone in Speaker Mode.

If you are able to avoid using the AudioManager specifically for these functions, this should help resolve the issue of the both the speaker and mic going dead when making a call (ie: neither the caller nor the recipient of the call can hear one another, even though the call is made).

Hope this helps

Impact Management Worldwide