Same problems: phone thinks it is "docked", or turns on S-Voice, all at random. Even "back" button haptics went AWOL for a couple of days! I have JB 4.1.2 with MD4 build. I tried cold reboots and several battery pulls to no avail. I even waited 10-20 minutes before placing the batter back. I also noticed the phone area close to the USB connector got abnormally hotter than usual.
The problem is two-fold:
1) Software: the "dock" mode page is part of the Page Buddy feature introduced with 4.1.2 (i think). To disable it, go into Settings >Display > Page Buddy > disable Docking Page. This is a band-aid. Does not fix the root cause but at least makes it less annoying.
2) Then, there is some sort of hardware issue, i am sure is related to the USB port. I air blasted it but did not seem to help. I then performed another battery pull and after reboot, it seemed fixed. Tried to make it "fail" again to no avail.
Was it the dirt, or did I wiggled something off when I pulled the battery this time? I dunno. To reproduce the problem, I re-tightened the two screws near the USB port, plugged a power cord into the USB connector and wiggled it and nothing happened. Will keep an eye on that area, especially considering how much abuse I know I have imparted to that USB connector.
Good luck
/lv