I've had a non-rooted HTC One X+ for about 1.8 years that started to experience an odd issue about a week ago. I hit the power button to turn the screen on (the phone was already on), however the unlock screen (default swipe up to unlock on HTC Sense 4) wouldn't respond to touch. The LCD, power button and volume rocker worked just fine (the LCD changed the time, the power button shut the screen on and off and the volume rocker changed the volume). It was if the digitizer wasn't responding (to anything)
I hit Power + Volume Down to force a restart. When the phone turned off, it didn't turn back on. So, I left it for several minutes (hitting the power button and waiting). Eventually it came back on (~10 minutes). I thought it was just a system lock up so I ignored it.
Several hours later it happened again and it's been happening again every couple of hours (but sometimes sooner if I take it out of my pocket more often). Sometimes, when I do the hard reboot, it restarts without issue. But sometimes it stays blank. If it stays blank I've found that slightly twisting/pressure on the screen causes it to start again (but I think it might be placebo).
I did a full factory reset and everything seemed great for about 3 days but then it started to happen again.
I found this answer and have enabled "Show CPU" and "Show Touches" and will post results the next time it occurs.
Is this a known issue (digitizer or otherwise). Because the phone is out of warranty, is the digitizer easy to replace? Could it be an app interfering?