Before I explain in detail, here's a list of things to check:
1. Battery voltage (at the battery itself under the rear seat)
2. Tire pressure
3. The transmission program button next to the shifter stalk is clean and the contacts for the shifter stalk are clean and corrosion free.
4. Transmission wiring harness
Now then, those are the main things to check. Here comes the details.
1. Proper Battery Voltage: These cars are pretty sensitive to battery voltage. Anything less that about 10 volts, the car will do wierd things. Make sure the battery is good and has a stong voltage of about 12V, +/- .5 volts. Try the "magic reset" (found on the main 7-series forum), this method has been known to solve some problems. If the problems come back after the reset, it is because your computers have relearned the problem the car is suffering.
2. Correct Tire Pressure: If one tire is not properly inflated, the brake/ASC sensors will detect the lower pressure tire as spinning to fast because it has a smaller diameter and the car will shift improperly. However, you'd notice this symptom only when the car is in motion, as you've said the car doesn't go into gear at all to get moving. But it's still good to check these things!
3. Shifter Stalk/S-E-M selector: After 199,000km's, these two circuits have seen a lot of use. The one you're probably most concerned with, however, is the shifter stalk contacts. You can take this out by following the instructions on the web site below. Clean off with electrical contact cleaner and let dry COMPLETELY before reinstalling. Quick question: Is the gear displaying on your dash?
http://www.nmia.com/~dgnrg/page_13.htm
4. Transmission Wiring Harness: Located underneath the car, this sometimes can wriggle itself loose and become dirty. You'll have to jack the car up and crawl underneath. Of Course, if it is dirty, it's a good idea to clean it off now while you're there. Disconnect the battery before you clean off and, again, let dry completely before re-inserting. I'm not sure where this connector is...I'll look for some pictures or write ups to help you out...
As always, let us know what you find. These are just the basics to check first.