HELP!!!

Was driving home tonight, and my radio went dead. Okay, no big deal, wanted an aftermarket anyway. Pulled into the driveway, turned off the key (now it is dark out so my headlights were on) and the truck went dead like it had no batteries in it. Turn the key on and the radio is still dead, but everything else works. ie: keyless entry, windows, locks, everything but the radio. Turn the key back to ACC. and the only thing that doesn't work is the horn and the radio still. But the truck will still start, and run just fine, minus the radio. I have checked all fuses, and relays. All look good. The only thing that I did today, was I found I had a blown fuse of my trailor lights and I replaced that. Other than that, all has been great until about an hour ago.

PLEASE HELP!! Thank you for any feed back.