Check with the switch assembly first.. because my window wouldn't close(yes on a rainy day too! what luck!), and the switch assembly was the culprit! In the ml design you can't just replace one switch you have to replace the whole assembly all 4 switches.. its a common problem..

a.) Replace window switch assembly by removing rubber liner from cubby tray, remove gear shift knob, remove plastic trim around gear shift.
b.) Remove coin holder, remove cubby tray, remove wood console by pushing up from cubby, remove cigarette lighter wire, than remove harness from switch.
c.) Replace defective switch.

let us know how you resolved this problem! plus you can't get a repair manual for the ml320, you have to wait 4 years after they stop production of the ml than they will release the service manual to the public, sucks... anyone work at mercedes sell us the copies =PP