If you open up the hood, look for two black rubber caps at the bottom of each wiper arm. Remove the cap and the 10mm bolt (if my memory serves me right) to loosen the arm. You might have to use a special wiper arm removal tool (BMW part no 61-6-060) to detach the arm and reseat it correctly. You could buy the removal tool from your local auto parts store. The BMW part costs somewhere in the neighborhood of $125!

When in rest position, measure the distance between the section of the wiper arm that is about 1/3 of the length of the arm (from the upper end of the arm) to the bottom of the windshield (top edge of cowl panel cover -- the black rubber lining in your pic). It should be approx. 51mm to 57mm (for the passenger's side) and 52mm to 58mm (for the driver's side). I could take a screenshot of the TIS that shows where the measurement is but I don't have the TIS disc at home. I could post it in the morning.

Hope this helps.