[AT&T Samsung Galaxy S 4 Q&A, Help & Troubleshootin] CPA Poke:
This happened to me last night, about had a major freak out.

First I have a couple questions for all of you who had this issue, so maybe we can pinpoint the actual cause:

1. Did you get any type of moisture (even just a little condensation) anywhere on or around the phone? Mine started acting up after I accidentally put my phone on the coffee table where some condensation had formed from a drink being there previously.

2. Any of you drop your phone at all? Even just a minor drop...as the day before I had a little drop (maybe from a foot off the ground), but I do have a case.

The reason I ask is because I started having this issue immediately after the phone was put on the condensation. Don't know if that was the cause, though, because I'm not sure exactly which of the steps below actually fixed it.

First I had to identify the exact problem...which I found by turning on "show touches" in Developer Options within the settings menu. This brings up a little white dot on the screen any time it registers a touch. Sure enough, I was getting "ghost touches" on the top left corner of my screen every 30 seconds or so - and it would generally last for 10-30 seconds or until I turned my screen on and off (that would fix it temporarily). The ghost touch was causing my drop down menu to pull down slightly every once in awhile, as well as not registering any of my other touches (including capacitive buttons). I knew the screen itself wasn't broken, because any addition touches were registering via the white dot - they just weren't interacting with the UI.

After doing some research online, apparently there are a couple main reasons that this ghost touching could occur:.

1. Faulty digitizer. Obviously this would Suck, and I really hoped it wasn't the cause. To repair would mean replacing the entire screen, as apparently the digitizer is attached to the screen and would be very difficult to replace by itself.

2. Any kind of moisture, whether water, skin oil, etc, getting in the cracks of the phone and staying under the screen, causing the pressure to indicate a false touch. Possible repair options included putting the phone near a WARM (but not too hot) surface for a period of time to hopefully cause the moisture to evaporate. Also some people said it just evaporated on its own after a few days (again, I hoped I wouldn't have to resort to this as I'm impatient and don't want to be without my phone for that long lol).

3. Software issue. Possible fix includes toggling HW overlays and/or GPU rendering.

Here's what I did:

Took the phone apart completely, made sure there was no visible moisture anywhere (there wasn't). Intermittently blew the phone (from the back and front, while it was disassembled) with warm air from a blow dryer. Left it alone, disassembled, for about 30 minutes.

Put the phone back together, booted up, immediately went to developer Options and (a) disabled HW overlays and (b) DISABLED "Force GPU rendering" (I actually already had it enabled).

BOOM - problem was gone!

So like I said, I'm not sure which of those did the trick - or which problem I had to begin with - but I'd be interested to know if anyone else had similar issues and/or fixes?