Guitar Hero 3 - Wii

We bought a bundle pack of 2 guitars for the Wii. It plays fine on single player. When we try to connect to multi player it loses the 2nd connection straight away. In 'select guitar' there is no guitar for the second one & the controllers don't work. I've done a search on the net & found a couple of other persons having similar issues, but no suitable answers

Any ideas ?