Only "Headphones" sound, no speaker sound after 4.2.1 upgrading
I can hear the sound from my iPad only when I connected to any headphones or bluetooth devices.
I tried many methods to get the sound back, starting from:
1. trying to plug in and out my headphone - nothing changed
2. switch on and off from the mute button (former is lock button) but it only showed "Headphones" or "Mute" sign.
3. shut down and turn on my iPad - nothing changed
4. Hard Reset my iPad and Restore - Still no sound, but I had to re-install everything again
5. Ask everyone and search every "no sound from iPad" topics but found none like mine.
However, while I upgraded the firmware, I noticed that I "locked" the screen during the process and I heard someone in the internet told me that it might be the origin of my problem.
I tried to sync my iPad and find how to re-upgrading the firmware again with no "locked" the button but there is no way to.
iPad, iOS 4