Tail Lights, Horn, Spoiler Malfunction?

[RobbieKnobbie]

I got a call from my wife the other day, telling me that my '06 Boxster S was honking its horn randomly and flashing its lights. There was a light rain that afternoon, and the kids were inside doing their homework (my first thought for the culprit is always the poor kids!)

I ran home and after a few minutes, it did indeed start honking and flashing its lights. The rain had gotten a little heavier.

I decided to drive the car back to work, where I keep all my tools and diagnostic goodies, but before I got out of my development the horn was on almost continuously, so Plan B: I went back home and disconnected the battery, and left it for another day.

Which is today.

As it stands right now, the car starts, runs and drives perfectly, but...
1. I had to disconnect the horn next to the battery (the one in the front of the car is fine)
2. the spoiler will not retract
3. When I shut the motor off and park the car, the tail lights remain on, in some seemingly random combination; the center brake light always stays on, the brake/directional lights sometimes remain, and the reverse lights stay on occasionally as well.

Obviously it's an electronic failure, I assume related to leaving it in the driveway when it rained, but where should I start looking, and are there any diagnostics for the various electronical control modules?

Thanks Guys!