Nintendo wii wont play game properly?

This is a wierd one but could any one possibly fathem this one out!?!?!? my 5 yr old boy has the new Ben 10 game (alien force) for his wii, he played it once and it was fine, but the next time we tried to play it the characters had developed a mind of their own and just keep gambowling around the screen on their own with out us even touching the hand controls making it impossible for us to play the game. I have changed the game (ben 10 alien force) at argos for a new one but the same thing happens, i've also tried the game in my neighbours wii and it is fine, i have tried everything like resetting the wii but to no avail. HELP!!