Well today the X5 wasn't cooperating with me.
I've been driving around since 9AM all over the city, and I garaged the X5 at lunch.
I went and took her out at 2PM again cuz I needed to do something. I stopped the car in the driveway, and shut the engine off. I went back to the house to get my sunglasses.
I come back out, and attempt to fire her up, and nothing!
The ABS and Brake lights went on, and other than that I heard this "clicking noise". The engine just wouldn't turn over. I tried again and same thing.
I tried the third time, and now everything electronic in the car was going on and off in sync with this clicking when I held the key for ignition. Everything - the radio display went on and off twice a second, every light in the car dimmed in sync too.
So I turn on the hazard lights and place cones around the X5, cuz I can't fire her up, and she's in the driveway of the townhouse building.
The tow-truck finally arrives after 70 minutes.

By then I appear to have lost battery power, cuz the blinkers and everything else no longer worked. The trucker hooked up his battery to the X5, which gave power again. We tried the ignition again, and got the same clicking sound.
X5 is in the dealer right now. Most probable cause is a dead battery according to my rep. I'll know tomorrow morning. I'd like to note that the clock display on the radio reset itself to --:--
So I think the computer of the car may have gone caput as well. I'll let you know tomorrow!