Are you using the arrow keys for movement, or does it happen with any keys?
Edit: ok, I've been able to reproduce it. Seems it only happens with the left and right arrow keys. If I hit the key again, it stops, though. You shouldn't have to exit and reenter the game -- just tap all the arrow keys. I'll fix it for the next release, though. Thanks for the report.
Edit2: Ok, I can see how after switching maps it would keep moving in one direction. Simply drop down the console and type -moveleft <enter> -moveright <enter>