it's an electrical problem... somewhere.
A girl I used to work with had half the electrical components in her car die spontaneously after putting subs in her trunk. The problem turned out to be that her "genious"
boyfriend used a couple inches of chain to attach the box to the top of the truck to prevent it from moving, and when she hit a bump the chain grounded the amp's power cable. My point is that there may be something simple but that you're not seeing that is shorting the circuit to brakes and plate bulbs.
Also bulbs can look fine, but be non-functional. Try replacing the bulbs, if they work after replaced, look for reasons they would have blown at the same time. (electrical shorts) If they still don't work after being replaced, you know for sure that the problem is in the wiring.
