I had this happen too after I received notice of some app updates. Two of the apps would not finish loading. I tried clearing the Notifications and shutting down several times. After many attempts one of the two apps finally installed the update, the other one which is ES File Explorer never would. I uninstalled the app and tried to re-install and nothing. Still in limbo on that one.

Also, syncing with Amazon books has become very flaky. I'm talking about Amazon purchased books which have always synced well. K4 NT syncs with K4PC very well. K4PC syncs with Fire. Fire and K4 NT don't sync. WTFire Amazon!!! To get highlights from K4 NT to Fire I had to first sync them to K4PC then sync it to Fire, and only after trial and error did hat work correctly. I think Amazon needs to hire some competent Android programmers!