I had a bad screen setup after flashing to 7/24 and needed calibration. My touches were all registering about half an inch too high. Had a failed calibration attempt, too. I rebooted a few times, and eventually got it set. I then rebooted again, went back into calibration and chose default, and things were normal. It was a pretty frustrating couple of hours or so, to be sure. I've had bad luck a couple of times having a custom calibration vs. choosing default, btw. Ghost-like movements stuck in a loop that are hard to get to stop (even with power-off/rebooting)... so once I get it working, I always go back and choose default calibration, and it's still been fine/fixed and the looping weirdness is gone.