Did you ever find the cause for this? I've got an '03 X5 3.0i that is cranking but not starting. There were no intermittent drivability issues before I parked it. The battery is genuine Bosch and is only a year old. I pulled it out and topped off the charge anyway. I also jumped 12V directly to the fuel pump leads under the seat and can hear it running. I also hear what sounds like a quick priming of the pump when switched to key position 2. I pulled the ignition switch out last night and gave it a through cleaning with CRC Electronics cleaner after popping the cover off from it. I'm going to re-install it tonight and see if that helps.