How to Disable Double Tapping?
My Galaxy S2 asked me to double-tap and drag to unlock (instead of just dragging) and every time I try to tap anything, one tap only makes a yellow box appear around the app or file or whatever, which is really difficult to deal with and annoying.
Could it be you've played with the developer options? Though I've never heard of that side-effect, the "yellow box" reminds me of some "feedback" which can be enabled there.
Go into the device settings, then from My device, choose Accessibility. From that menu, press TalkBack, then click the switch in the top-right corner to turn TalkBack off.
After tapping something once to get the yellow box (and the spoken description of what the thing is), double-tap anywhere on the screen to click the highlighted thing.