As the Wii seems to feature on here quite a bit can anybody help with a problem that has developed with mine?

The controler when switched on lights up the 4 blue lights at the bottom of the controller for a few seconds then they all go out and we are not able to register the pointer on the screen etc - in fact the control does not work at all. I have replaced the batteries and tried pressing the red buttons on the console and controller to syncronise them, but that did not seem to work. However, I only tried to do this for a minute or so - should I try it for longer?
So - any ideas??