Why won't my Rock Band 2 drumset work with Rock Band 3?

My rock band 2 drumset's green pad only works around 5% of the time... I can't enjoy the game when I continue to miss this note! I've heard that other people experienced this problem. I was wondering if there was any way to fix this problem, as I can't seem to buy Rock Band 3 drum sets anywhere and where I can buy them they`re way overpriced. Thanks for listening...