No, that resolution doesn't work, either. I'm having the same issue, and have tried the same variations (as well as the other thread link provided, above), all to no avail. Same OS and graphic card as karsten.
any other ideas?
First, look at what Sardaukar wrote above - you must re-type the dashes rather than copy them from the documentation. In the doc they look like dashes but are actually another ASCII character.
Second, if all else fails try formatting the resolutions specs like this:
Obviously make the numbers be whatever you want, but notice the 'f' that is in there now. It might not work for your PC, or if it does, it might mess up something else in the graphics.