What's up with my record button? MPC 1000

I'm running JJOS 2XL on my MPC 1000 and when I press the record button, record flashes once and then the overdub light comes on. Then once I start playing my samples on the pads and play it back, everything I previously played, plays back all at once. This shows up just as on dot on the graph which I have to keep erasing.

Any help? Thanks

http://www7a.biglobe.ne.jp/~mpc1000/os2xl/click3.htm

Check these settings