I have the same issue - It DOES seem to be triggered more often when trying to climb through a window when holding right mouse (for combat stance), but I've also had it happen when I wasn't in combat stance. I just climb through and end up on the other side - frozen in place. Zombies don't seem to be able to attack me. They SEE me and run up to me, but can't damage me. ** EDIT ** I've had the freezing in place issue come up while doing other activities, but I'm sure it's because I need to right-click things to do them. IE; I right click on a window to get the menu to pop up (this puts me in a combat stance, even though I'm not holding it down). When I left click to put up a curtain, I freeze up. This doesn't happen every time, but has happened more than once.