Kind of sounds like it may be the drivers door latch??
Have you tried to use the mechanical key in the drivers door lock? Usually the key is 45 degrees for electrical control, 90 degrees for mechanical control.
Also could be a problem with the GM or Footwell module relay(s) if it is somewhat configured as the E46/E39/E38?
Might check out this site:
www.bmwgm5.com
Not sure the E70/E90/E60's have started to act up as much as the earlier chassis, but Scott may have info on the later models on his site.
Let us know what you find in at the end of the day.
Any BTW, the BMW Central Locking System is anything but simple!