I had the exact same problem...but it was when I put the car in reverse... I dunno...could be the same thing.
Look at the wiring harness in the trunk. I know it sounds odd, but this could be the problem.
The wiring harness for the rear signals and reverse lights runs by the trunk hinge. My harness was cut or worn thru right near the hinge where it was clipped to the frame. Because of the flexing motion when opening the trunk it split the wire, eventually causing a short. such that everytime I put the car in reverse I would blow the fuse that controlled turn signals, reverse lights, heating & cruise control (12amp)
It could be this simple - like I said its a starting point
