I have a Samsung Note 3. For the last 2 months, I can download APK files - for example, just downloaded the new Google Play Store here: http://www.androidpolice.com/2014/10/09/breaking-google-play-store-update-5-0-31-adds-even-more-material-design-highlights-and-moves-whats-new-to-the-top-apk-download/ and it's on the phone, but when I open it and go to install it, when I touch INSTALL - nothing happens. It's there, but it won't install. This happens with any APK. one caveat: in the past if I've rebooted into safe mode - which of course means with no downloaded apps running - then and only then can I install. Some 3rd party app might be blocking me from installing. That's all the info I got. Can you help?