Unhappy [Q] Touchscreen not responding

Hello guys, I need your help.

Today, out of the blue, my wife's ION (lt28at) touchscreen stopped responding. The phone boots just fine (perhaps a bit slower than before, but that's my appreciation), messages are received, apps update automatically, but it doesn't respond to touch. How could it happened? we were just arriving home from a running workout, we were sitting on the porch and the phone rebooted on its own, after that it stopped responding to touch.

Now I've got a very sad wife, very little chance of getting a new device (the market in Venezuela is very restricted and limitative), and no clue as to how to fix it.

Please if any of you can help me here, it will be most appreciated.

Edit: Forgot to mention. the device has its bootloader locked. Firmware updated to ICS 6.1.C.1.111. Rooted (probably about 9 months ago).
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We are what we repeatedly do,
excellence then is not an act, but a habit
- Aristotle