Last week, the VSA, traction control and brake warning lights all came on in the dash. A quick search online showed that the brake light switch (next to the brake pedal, under the dash) could be the culprit. I checked the brake lights and they were working fine, so the switch was working. I suspected a sensor.
The light came on, again, a few days later. Still no problem driving the car, or braking, and the brake lights checked out when I got home.
THEN, over the weekend, I started the car, but couldn't get it out of park! I checked the brake lights and they were NOT working. I kept trying and trying and eventually, the switch started working again and I was able to drive home without being stranded!
I replaced the switch in about 10 minutes (it takes a 14mm wrench to loosen the locking nut).
I figured out that the lights were coming on when driving the car and likely coming to a stop, but the brake light wasn't working, so the computer is sensing the wheels have stopped, but the brakes aren't being applied, so that indicates a problem.
And, of course, the computer enforces safety by requiring you have your foot on the brake before shifting out of Park. If the brake switch isn't working, it can't tell that you have your foot on the brake.
If you replace the switch yourself, make note (take a picture!) of where the nut is on the shaft of the switch and that will help you get real close to the proper adjustment.