I had that problem with my 07 750. It was under warranty, so they replaced some type of electronic module on the transmission and it fixed things. I want to call it the ECM but I can't recall.
2011 750i Jet Black / Ebony Interior / Black Ash Wood Trim
Factory Options: Luxury Seating Package / Premium Sound Package / 19" Alloy Radial-Spoke Wheels / Rear View Camera
Aftermarket Options: 30% Ceramic Tint / PIAA Xtreme White Angel Eyes / DVD In Motion