Mpc 2000 classic - recording problem

I'm working on an mpc2000. Lately, I will record part of a sequence and,when I go to do an overdub, I will not hear a sound after the record button is activated and the pads are hit. If I stop the recording and then hit a pad, they immediately work fine. I am wondering if I have changed a setting or maybe I don't have enough internal memory. I have no idea. Can anyone help?

It is possible that the previously programmed sounds you are trying to dub over may be assigned to mute off whatever new sound you are trying to record. Maybe this is your problem?