I'm having a similar problem. What I can tell you is that there is another 20 amp fuse under the hood that also controls the dash illumination, security system button, cigarette lighter, etc. Mine keeps blowing repeatedly and the dealer can't replicate the problem.

I had a cell phone charger that basically fell apart in the lighter and I later found a piece in the lighter slot. Even after having the lighter replaced (I broke it and the mounting trying to get the piece out), the fuse continues to blow. It doesn't blow right away and usually doesn't blow until I've been driving a while. I do have the lights on during the day and the climate control and radio are also on at the time.

The frustrating piece is that the fuse controls the security system (I keep walking away without locking the car) and the tail light and dash lights make it very difficult to drive at night both from a getting pulled over standpoint (can't see the speedometer) and from a safety standpoint.

Any other hints or ideas to have the shop guys investigate would be much appreciated.