ABS light problem is fixed. Here's a review of my findings.

First Mercedes "specialist":

- First new brake switch installed was faulty. It failed thirty miles from home. I drove back not knowing my brake lights had been on the entire time (remember this part).

- Second new brake switch installed. Seemed to fix the problem -- for a while. Then the ABS light came on again. Same basic problem as before. Codes read "brake light switch." Weeks later I started getting a bulb warning light. Replacing the brake light bulbs turned it off, but the problem would surface in a few days.

The shop showed no real interest in helping further. They said: "Make an appointment next Thursday. We'll have to keep it for a few days -- maybe we can find the problem. Probably an ABS control unit."

New Mercedes specialist -- a real one:

- Called a new mechanic. "Hans" asked for me to come over immediately. Took the time and interest in the car. Spent an hour right then to read the codes, drive car, re-read the codes. It came up every time "Brake light switch." He put in a third new switch. I also mentioned the brakes lights had stuck on for thirty miles. We inspected the rear multi bulb housings very closely. They appear to have slightly warped/burned areas where the bulbs are held. Possibly this now causes a high resistance situation, hence a bulb out warning when there isn't one. We replaced both units and installed all new bulbs.

End of problem! I have driven the car for about 150 miles and all lights stay out.

The problem got complicated when the fist shop installed a questionably "new" first switch. I say this because they showed it to me before they put it in. The bag had already been opened. My sense told me it's not 100% new. It was just a hunch, but look at the result. Keep this in mind when your ABS light goes on and you think replacing a suspected part with new instantly solves the problem.