"sync disabled" and "unfortunately S Planner has stopped"
I had the same problem: S-Planner and email would not sync. In the sync settings was also an item saying "master sync disabled" but no indication as to how to enable it!

The fix for me was to go to the options menu of the phone (when you swipe your finger down from the top of the screen). You should then see a few green and blue symbols (bluetooth/wifi etc.). At the top right there is a gear wheel icon and next to this on the right is another button which when clicked will show all the different icons for your phone settings. Press this and look for the "sync" icon. If it is disabled (blue) then click to enable it.