PARK LPS (15a) Fuse Instantly Blows
 

While driving through a tunnel today I decided to switch on my running lights, I heard a pop and a few seconds later I got a SVS light.

Got it home and narrowed it down to the Parking Lamps fuse (#45 under the hood) which was blown. I replaced it with a new 15a and it instantly blew, so I unhooked ALL of my custom interior lighting and added a 20a (no more 15s) and it still blew.

Does anyone have an idea of what could be causing this? Obviously something is grounded somewhere but I have no idea where to start. Everything worked fine last night and nothing has changed since.

What I have:
High and low beams
Brake lights
Turn signals / Hazards
Reverse lights
Courtesy / open door lighting

What I don't have:
Corner lights
Running lights
Fog lights
Interior lights (gauge cluster, prnd321, etc.)

check all your grounding straps, give them a wiggle, see if any are loose, and make sure they are not contacting any of your other wires, its clearly a short to ground somewhere in the circuit. here maybe these will help...
Courtesy lamps

Exterior lamps

Interior lamps 1

Interior lamps 2