We have exactly the same problem. We also got our Wii for xmas and all has been fine until yesterday.
The remote has gone nuts!
My husband discovered this when playing Tiger Woods golf.
The remote doesn't recognise when he is pointing the controller down - it works in all other capacities so it isn't totally not working.
When we tried bowling, we can bowl, but the bowler just lobs the ball, as opposed to swinging his arm back and forth. The remote simply doesn't recognise when the remote points down towards the ground.
PLEASE HELP. WE ONLY HAVE ONE CONTROLLER SO NOW WE CAN'T DO ANYTHING AND MY SON IS HAVING A FRIEND ROUND TODAY TO PLAY Wii.............