I am not getting any sound from my center speaker...

Question

I have a sony STRDE575 receiver, hooked up to a PS3 through optical cable. I turn on the receiver do a test tone on it and I get sound from all the speakers. I put on a movie and from thirty seconds to two minutes i lose sound from the center speaker. I have replaced the speaker wire, checked the actual speaker, changed settings from micro speakers to normal and i still lose middle speaker sound. Please advise!!!