One problem related to engine belts and pulleys has been reported for the 2003 BMW 540. The most recently reported issues are listed below.
Started the car and began to drive out of driveway when I heard a noise in the engine. Shut down engine and popped the hood- found drive belt shredded because power steering pump snapped and let loose into tension pulley- luckily I was not at speed and belt did not fail- otherwise catastrophic engine failure would occur along with loss of power steering.