OK, I'm at the end of my tether here. Just hoping someone can suggest what can be wrong and a possible solution.
Here's what's going on. In December, I bought an iPad 4 (wifi, 64GB, now with iOS 6.1.3). For about three months it worked perfectly well and I was loving it.
A few days ago, I started noticing that the screen sometimes wouldn't immediately react to my touch when waking up. I couldn't swipe to unlock. It took a second or two, but then it seemed to be OK. It didn't happen every time, and once it was on it worked fine, so it wasn't too troublesome.
A couple of days ago, when I opened the case, the unlock screen came on as usual. But the screen was completely unresponsive and stayed that way. I tried resetting a few times with the sleep/wake button and the home button and the iPad restarted but still the screen was completely unresponsive. Rotating the screen worked fine, but the slider was unresponsive on all four sides.
So I finally decided to start up iTunes in Windows and did a restore from backup. Hooray! After the restore the iPad appeared to work fine all day. The screen seemed to be responding perfectly.
And then... next morning, as I wake up the iPad, once again the screen is completely unresponsive. Again, restarting/resetting it does no good. I do another restore from backup, and again it seems fine. For a while... Once again after waking up the iPad after doing so a few times with no problem, the screen is completely unresponsive. By this time, I decide more drastic action is needed so I decide to do a restore as new followed by a restore from backup. Of course there's stuff that's lost, which is a pain to get back. But as the iPad comes out of the restore process, the screen seems to be OK again.
Except after using it for a while, and waking it up from sleep after a few times of doing so with no trouble, yet again the screen doesn't respond. Argh! I can't understand what can be going on. When it's working, the screen works perfectly (so I don't think it's a hardware problem), and it never becomes unresponsive when I'm using it, just sometimes (not each time) when I wake it up. But I can't understand why the restore to new didn't fix things, if it's a software problem. Could it be somehow related to the update to iOS 6.1.3 (it hadn't happened before that)?
Another clue: the last time this happened, I planned to do another restore, so hooked up the iPad to my laptop. iTunes did the usual sync. I think I may have hit the sync button again before I was planning to do a backup. The interesting thing is that after the sync (no backup or restore) I try the iPad again and the screen responds and is OK for a while! Very weird.
Any ideas for what could be going on? Another issue is that I bought the iPad in the US but am now spending a year in Mexico so getting it to an Apple store isn't easy, and not sure how the warranty will apply here...
Any suggestions greatly appreciated!