hey man
u probably didnt get any answers cos your title isn't descriptive enough..heres a link to check out. theres another very descriptive one somewhere that i cant find anymore - perhaps someone else can relink it.
viewtopic.php?f=15&t=153012in summary - the buttons die all the time. u only need to replace the mode button's tact switch on the pcb with the part ALPS skhhaka010 that you can buy yourself from various places depending on where you are... its an easy solder job for you or someone you know once you have the part and theres a few links in the 'mpc customisation' sub forum about changing them over.. but buy more than 1 cos other buttons will eventually go
or you could just buy another entire pcb board from mpc stuff but they are sold out at the moment.
quite conveniently i actually have some spare switches i can sell you depending on where you are - they're cheap to buy new from places but the postage is always brutal. if your interested send me a PM