I have the latest version of DOpus (9.0.0.9 -- btw, why can't I see the version number from Help->About, as in every other software?). However, I can't find that "Select previous folder when going Up option".
The only thing I can find is the old underline option:
The version number should be shown directly below the Opus logo at the top of the About window. Could you show a screenshot of your About window? Maybe something goes wrong on your system.
See below, though it looks like this option is missing from your version. Maybe a problem with the German translation, or you're not using the version you thought you were?
Something has happened to the command definition of your About command - go into Customize mode and edit that menu item. The command should be Help ABOUT.
Did you reboot after installing? If so and it didn't solve it you should mention it to H&P at their forums for the quickest response. (Or email them directly. I'm not sure what their support policy is.)
Ok -- rebooting (actually I didn't but instead renamed some temporary language files did the trick. The broken umlauts are gone, and the "go up selection" option is there and working.