Yeah, thanks! =)
That really was the problem! Now I'm on an other computer and suddenly it works!
I've tried a lot combinations and caching can definitely be the reason.
But in general:
Am I right that "MyModel>title" is just temporary at this moment (during loop)?
Is this and all possibilities (static behaviour, behaviour in loops, etc.) of binding conventions clearly documented somewhere?
That would be great.
But this topic is now solved for me! 
Thanks for the help!
Dominik