I've had a similar issue with rear tail-light bulbs and the defective bulb on my display. Last week I went through all the bulbs in the rear and lubed them up with di-electric grease ($2.00/ tube @ NAPA or wally-world).
All the lights are back to normal and no more defective bulb errors.
Still have a defective display error with the little boxes though. Anyone else here have any more input on this without a full replacement? What I would really like is someone who just cracked up a 98-99 e300td with 60k miles and wants to part out a dashboard!!
PMU