sample pad problem, please help!

Hi

I got my new mpc 2500 a few days ago. i am finding that when i hit more then one pad at a time one will cancel the other out.
the sounds that come with the 2500 dont do it, but audio drum samples iv put in do. it is really getting to me now and im thinking of returning the unit. am i doing something wrong here? is the a setting i need to change within the machine.
iv had a 2000xl for years and i havent had anything like this happen.
would haveing a new operating system be of any help? how do i find out what operating system i have?

thanks

thanks for that mate. i just looked on the mpc 4000 part of this site. and there was someone with the same problem. i just went into programs and changed mono to poly. very simple lol!

thanks

Hello John L.

Life is very simple.

Please listen to me when i say "Don't make it complicated" all the best sunshine .

Sorry to get all Stephen baldwin on you