1.1 was renamed to 1.5 shortly after I made that post. So you have the version I intended.
When you get the CrashCatcher dialog, please add a note saying that you are trying to upgrade from 1.0.3 (and also mention that you're running in German) and email that crash report to us.
I'm not sure what's going wrong for you, so I encourage you to contact our support ninjas at
omnifocus@omnigroup.com so they can get the details and help resolve your problems with upgrading.