Ha! Just got that error from my last post fixed.
As I postet before (Exactly here)
I'm linking the MFC staticly to my projects to prevent the users from installing the Visual Studio runtimes if they want to play my future games.
Turns out that if I set the MFC linkage to 'dynamicly' everything works fine.
They now share the same 'STL Pool'.
The only remaining question now is what's about the vs runtimes now? :-/
I guess I have to figure that out tomorrow...
Good night, internet.