Open the hood and have someone else try to start it, are the belts spinning?

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.

Just wanted to update this with what I found. Cleaning the ignition switch didn't fix my "cranks but won't start issue." I tried both keys, depressing the throttle to the floor, nada. Finally I tried disconnecting the MAF as I'd seen suggested a couple of times on here and wala, roared to life. I had been quick to rule it out because it had been said that the MAF is not in effect during startup.

Now I need to figure out if it just needs to be cleaned or replaced.

Cleaned the MAF with leftover CRC Electronics Cleaner QD from when I cleaned the ignition switch and am happy to report, in the words of Borat - "Great Success!"