check your rca's... make sure there tight at the back of your h/u and the amp... also check to make sure it didn't get cut anywhere throughout the car. do the speakers put out any sound?? depending on your amp you might have a choice between rca and highlevel input.. make sure it's on rca... unless your using highlevel of course. Also check your gain levels.. check the wiring to all the speakers make sure no part of the wire is touching any metal... those are the only things I can think of.

Let me know how that works out!

-Chris