JuFro: Yup so I click on the ground to move, and my character teleports randomly toward it, while the walking animation plays sometimes, sometimes he walks in place for over 2 seconds. Restarting my computer did not help, and it only happens in multiplayer
This sounds like the lag-monster. It's one of the top character-killers in NWN.
I'm not sure how you ruled out lag, but I've seen the same thing many times in NWN1 (haven't played much mp in NWN2) and it's caused by lag. It usually presents itself when you join a server with a long ping time or a lot of people on it. But sometimes it just happens (perhaps the server's computer is busy doing something).