Try walking through the basic setup on the receiver. Many of them have options to select whether you are using center and/or rear speakers. They also usually have a level adjustment for each speaker. Put on a 5 channel DVD or SACD and put your ear right up to the center. If you don't hear anything, but the speaker is on and level adjusted similar to the other speakers and the wires are correctly hooked up, you probably have a receiver problem.
