I'll throw out a couple of suggestons.
Check for any fusable links from your power source to the fuse box and check them out (not just visually, use a meter or light to check).
Check for any wiring connections that may have been knocked loose or cut when you were removing the cd player.
I'm betting that a fusable link was blown during your repair. Or another fuse leading into the fuse box. (I'm only guessing because of the unknown vehicle and it's wiring system). Now you know to disconnect the battery or powersource when doing any type of electrical repairs on the vehicle (just as a safety precaution for you and the vehicle).
Get a wiring diagram if you can't locate any links or fuses.