Thanks GST, good luck with the new phone. I'm probably going to do the same thing. I keep mine dry, I know it's not water causing my issues. Such a PITA especially since there's no new Droid I really want.
ok so i went on a trip for about a month and a half, and left my phone in the car after getting to the airport, it sat in the car while it was freezing cold and snowing until someone came to pick it up (not sure when that was im guessing after a week or two) when i got home and went to turn on the phone the screen did not work, at first i thought it was a software problem, i had miui for a long time and had installed cyanogenmod just two days before the flight, i did not have the chance to mess around with it because i had forgotten it in the cat, so i went on and installed the miui back thinking it would fix it if it was indeed a problem with the rom.. but it didnt help.. i searched and searched and the only solution i could find is to bring it back to repair at the company.. but the phone was bought in another country and i do not have coverage for it so thats not a possibility..
then i found one post that said the problem is probably moist that has build up between the screen glass and the touch screen! it could be due to taking it in to the shower with you, or as i did leaving it in a freezing cold car for a week+ whatever it is it seems legit.
so i kept searching and finally found a post that said that if you press the screen down really hard it will fix the problem temporerly, and it sure did!!! when i press it it works fine, it then goes back to being crazy calling random people and writing random letters without stopping after a few seconds but when i press again it works fine again, so i am guessing the moist theory is right.
the next comment i found said to replace the glass on the screen, its called a digitizer and its the top glass that the moist is trapped under it (and may be loose which prevents the touch screen from sensing your touch) i found it on ebay for about 13$ and it comes with everything you need to replace it including the screen, you can then go on youtube and fine videos on how to open the phone and exchange the screen.
anyways try and do the pressing thing, if it does help its probably a moist problem and replacing the glass might help (maybe just pressing it to stick together will help by it self)
hope this helps and good luck to us all