Locking Problem

[bloggs24]

Hi, Just noticed ive got a bit of a problem with the XR6. When i close the doors and lock the car, the car beeps as if a door isnt closed properly and unlocks just the drivers door, and because i assume the car thinks a door isnt closed properly the interior light and the ignition barrel light stay on, i can hold down the drivers door lock to lock it, but the interior lights remain on. I'm completely stumped as to what the problem is.
Dunno if it could be related, but the only eletricals done to the car is the subwoofer and amp i installed about 2 years ago. i took the car for a drive and while driving i could hear a tick, almost similiar to a sparking noise under the drivers seat which is where i had run the power cable for the amp, also around the same time, during the drive the interior lights would flick on and of. im going to pull up the carpet tomorrow and have a look, atm though i've pulled out the interior light bulb, but the ignition barrel light is still on, should i disconnect the battery so it wont go flat? Also any idea on what my problem could be.