Windows Live Writer Server Error 500

I like to use Windows Live Writer as Blogging tool and in the past it always worked fine.

But.. (there’s always a but..)
Now, for some strange reasons, I get the following error message when I want to publish something:

the server reported an error with the following web address 500 internal server error

I already have seen lots of solutions, some technical and some..  Well, let’s say IMHO a server level exorcism is not needed here

None of the solutions helped to solve this problem, so that is why I blog about it.

Maybe one of you knows the answer to this weird problem