Using the mpc with a midi controller...

Hi - I am using a Kurzweil PC2x keyboard to control the sounds on my mpc2000xl and I am having problems using it once I lock the note repeat function... what happens is I'll have one note held down with one finger on my kurzweil (yes, I use the "shift - note repeat" option so that it holds indefinitely) and then try to play other notes but after I have touched another note for the fourth time (yes, every time it is the fourth time of hitting a different note), the original note I was holding, turns off... but i don't want it to stop holding no matter how many other notes i play! is there some polyphony issue or something in the program/pad assign i need to change? also, i'm pretty sure the problem is not with the Kurzweil b/c I used a different controller and the exact same thing happened! please help!
thanks,
Jon