Hi Moritz, that error message looks like it's from the startup script here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=8064.8

The problem you're running into is the one I described later in the thread here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=8064.12

You'll need to remove that file from your app data startup directory.

Please note that all the problems you are describing here are from interactions between extensions that are not part of the regular MoI install and are not supported by myself directly.

- Michael