As far as possibilities of issues...
Could be the switch panel (can be ruled out if the remote fob doesn't work).
Could be the window regulator motor itself (dirty motor brushes). -assuming only one window doesn't work...
And then there's the umbrella issue of having a flaky connection in a wiring harness or solder joint in related circuits.
Do you not know anyone else with a similar car? It's easy enough to pop the switch panel off and try. Or ebay a used one.
http://www.ebay.com/itm/06-07-08-BMW...ht_2925wt_1144