On my 540I it looked like I had both a rear main seal and crankshaft seal leak after I changed out my valve cover gaskets.
Turned out to be the vanos solenoid gaskets leaking oil down the front of the engine not the front crankshaft seal. (from what I hear these don't go bad very often)
Also, the intake manifold gaskets were bad and the small hose connecting the crankcase vent valve under the intake manifold was split allowing oil to drip down into the valley pan area and running out the weep holes in the back of the engine that looked like the rear main seal was leaking.
About $75 for new intake gaskets, and vanos solenoid gaskets along with about 2 hours of labor, and she is once again oil leak free.