DVD player might be a dirty lens. It might also just be a dead player for some reason; the mechanism is likely very similar to that of a $20 DVD player from a big box store, and hooking a cheap one in to the system if possible might be the most cost-effective and and least difficult way of resolving the problem.
Speakers might be control settings (check the fader and the balance controls, and any switches you have for sets of speakers), or a loose wire going to the speakers, or a failure in the amplifier, or probably a few other things.