>I don't think this is heat related as switching the screen off and on again clears the issue.
I'm talking based on a very rough understanding of how capacitive multi-touch works, but it seems plausible that on restart, the screen calibrates itself for the current environment, "zeroing" itself according to the capacitance it is currently seeing, and that that zero value is no longer accurate once the temperature changes significantly.
As someone that works on projected cap screens, I can say that you're pretty much on the mark. You normally take a "baseline" or background read of the sensor's capacitance and then use the signal level above that baseline to determine the presence of a finger.
Now if you don't keep dynamically adjusting that baseline to the environment, and there are many different approaches on how to do this, you could start seeing false touches or no touch at all.
That being said, every modern manufacturer has algorithms like this in place. So another place to look is construction. When you see problems on the edge, is the flexing of the screen causing your glass to delaminate from the sensor line? Perhaps power cycling fixes it (for now, because of dynamic baseline recalibration), but eventually the circuit could completely fail from a mechanical point of view. I'm curious to see if the problem grows and if it eventually results in failed units that software can't recover.
{edit} Looking at the teardown, Nexus7 is using an Elan controller. Out of all the teardowns I've seen this is the first I've seen from them in a major product as opposed to TI, Broadcom, Atmel, or Cypress. This might get interesting.
Interesting - I have an iPhone 4S, and I've noticed that if it's in my pocket, the touchscreen is really unresponsive. I get a call, pull my phone out, and it takes several tries for the "swipe to answer" gesture to succeed (usually the iPhone will drop my swipe about halfway through).
The incoming call probably makes this worse, when I am not in a call I don't recall ever having trouble unlocking my phone with the same gesture.
Was the screen facing your body when it was in your pocket? You just had a very large capacitive body next to the screen for an extended period. What you described would make sense if the iPhone's screen recalibrates itself.
This appears true. I have a Nexus S and I have seen some times that the touchscreen freezes after I finish the call. It usually happens on a hot day and if there is sweat on the screen. When I press the power button and unlock again, things are back to normal. Have checked with some of my friends who use iPhone and they do not seem to have experienced such issues.
A software defect the affects the same portion of screen regardless of orientation and that is temporarily fixed when physically turning the screen off? I'm not convinced.
Hopefully Google/ASUS will respond well with fixes. It really does sound like a heat-related issue affecting the digitizer.