why don't my inputs work on my tv anymore?

for some random reason the inputs on my Conia CPDP3201 plasma don't work anymore. I have tried the HDMI and normal RCA inputs and S video and nothing works. I wonder if the source function has died. Although it does work on TV. But pretty boring without set top box and dvd. I have purchased new cords to do this and plugged the dvd into another tv and it works fine. I have unplugged and plugged, reset the tv and can't think of anything else. Some of the inputs, like the rca and s video hadn't been used prior to this. We just used HDMI, so they can't have worn out or something. Please help.