I had similar experience with the tail light sockets on my C230. In my case the solder "bumps" on the bottom of the bulb had worn and the socket contact's "fingers" didn't have enough spring force to make good contact. I got the bulb out indicator. In my case the bulb did not light up so it was easy to find although a little confucing at first when I found the bulb was good.

I would definitely agree with above posts to take out the tail light bulbs and clean/inspect them. Many times I have read similar posts about fuses "I took them out and cleaned them and put back in and now everything works."

Might not work but well worth a try.

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra