So after months, i've found something : the wiimotes buttons don't work in certain games if in the config>gamecube the game controllers are not put on "nothing"!!!! Try with dragonball z tenkaichi and smackdown vs raw 2010 and you will see!!!! This is an issue i hope will be resolved!
Did you try removing the batteries and putting again? That works for me...
It could be how the game is designed. TvC won't let you use wiimotes if any Gamecube controllers are connected.
Yes, some games use the pad before the wiimote so if you let in the gamecube config a controller, the wiimotes don't work in game! There is the same problem with the real wii