dead radio and interior lights on 1999 Acura RL

i have a 1999 Acura RL. Power to the radio and interior lights is dead. i checked the interior fuse box but did not see any blown fuse. i checked the under the hood fuse box and saw the interior lights fuse(20A) blown. i replaced the fuse and the interior lights came on. i turned the ignition switch to ACC and the interior lights went out and the fuse blew. what is causing the short? is this also causing the radio malfunction? thx