PCR500 and Sustain Pedal Problem...

  dear folks , I just ran in to a problem with my PCR-500 and Sustain Pedal.... when the pedal is unpressed the notes are sustained but when i press it , the notes are not sustained , it`s like working reversely.... i reset my PCR-500 but the problem still exists.... i pressed the pedal and then turn the PCR500 off and turned it on while the pedal is pressed but again the prob. exists..... where do you think the problem lies in?!! Your help would be really appreciated, Joopin