Is a character encumbered? If you switch leaders, can you move?
A couple people reported a problem with crashing when trying to move when encumbered, which I could reproduce in specific circumstances:
If the hero is leader and I open the inventory, switch to the DK and drop item's onto the hero's portrait until he becomes overloaded, trying to move after that will crash the game. If I switch the DK to leader first, open the inventory, drop items on the hero's portrait until overloaded, then everything is fine and he just can not move (as intended).
If that is the problem, offloading junk to sell (and excess food and trap/alchemy material) onto a summoning doll should help. The act 1 doll can use a crossbow, so doesn't need to be able to move, if summoned away from direct combat.
I also tried this in a new game, using a chest and a couple barrels dropped onto portraits. Dropping onto the follow's portrait was fine, the leader would crash trying to move (directly from the ground, or from the follower's inventory). The disk version was fine either way.