I don't know if this helps in any way: I was playing version v4.1.1.4145012 and had to restart yesterday because the main quest stopped progressing in Act 2. I have version v4.1.1.5849914 installed now and I can't move the characters either (after loading). I deleted the old savefiles and started a new game, but once I reached the ruins to the right of the map in Act 1 (where you find Withers), my main character got stuck again. When I switched characters, they got also stuck after a few seconds of movement. Restarting the game helped, but the bug occurs again occasionally. It's similar with the menues. Seemingly at random, the menu, camp button and save/load screen stop working. Forcequitting and reloading helps.
The only tip I can give is to save often and to not start honour mode. The game is very bugged in general and usually new patches mean more bugs (and/or old ones reoccuring). It's especially tricky if you update during the playthrough. You have to be very patient ):