Trouble Playing Back Tracks

Hi
I have just recently bought an MPC1000 & really enjoying it untill i came up against this problem!

So,i have a very basic sample recorded & and a beat,both tracks are playing fine Solo,no problem but when i try to play both tracks back together they seem to be cancelling eachother out and i can only hear certain parts from each track(REALLY ANNOYING).it seems to be making a clicking noise when thier played together,where the actuall sounds are supposed to be.Also when trying to record the sample straight onto the beat or onto antoher track,the pads become inactive and really glitchy,not letting the sound through.Hope you can understand.

Am i missing something?
I have searched and cannot find anyone else experiencing this problem,any help will be much appriciated!!!
Thanks

place the sample in the drums in 2 different programs
or
make sure the program is set to poly(its in the manual)

Thanks man!!!!

My program was set to poly,just placed the sample and beat & in different programs & quickly tested it and it seems to be working.

Thanks for the help man! Much apriciated,back in studio 2moro