I did mean clean it with a brush; However, the problem continues.

Now, if I turn the key to #2 position when I first get in, put my seatbelt on, then start it seems to start every time (knock on wood).

I think it has more to do with giving the fuel pump a chance to pressurize the fuel rail than the seat belt.

I had a '91 Jetta. When the fuel pressure reg failed it had the same symptoms. I'm still unclear how the fuel pressure is regulated on the X5. I know there fuel filter has a check valve; but that doesn't regulate fuel pressure. if the system is regulated by a pressure switch (turns pump on and off) it could be that also. I will be looking into it more today and I will let you know.