Accelerometers are probably stuck.
http://www.nintendo.com/consumer/sys.../wiiremote.jspQuick tip: Cursor (hand) or character movement not responding properly?
Hold the Wii Remote with the button side down. Without using much force, firmly tap the button side of the remote against the palm of your other hand a few times. Doing this does not take a lot of force, so be sure not to tap the Wii Remote very hard. Check for proper response. If the problem is not solved, please follow the rest of the instructions on this page.