Holy dead thread revival!!!
I had the same problem: low beam malfunction on the passenger's side.
I swapped bulbs and the passenger's side still didn't work. So my problem wasn't a dead bulb.
I swapped the wiring harness that goes from the control unit to the xenon, but the passenger side still didn't work. So that wasn't my problem.
I swapped xenon control units (#8 on this schematic:
http://realoem.com/bmw/showparts.do?...63&fg=05&hl=14) and then the driver's side was dead. So that was my problem. Dealer wanted $167 to figure that out.
I bought one from the dealer (that stung) and installed it this morning.
Fortunately, I was able to remove the control unit without having to remove the headlight. It was tricky, but possible.
Some people have said they were lucky and their problem was just the small 2 prong wiring harness that plugs into the control unit. I was not so lucky.
Just some info for anyone else that has a problem and stumbles on this thread.