Found the problem!: It was a category.
I've a category on UIView for searching inside subviews.
I had a method named
- (BOOL)containsView:(UIView *)aUIView;
Which was breaking the behaviour. Changed the name of the method and now it works fine.
I don't know, but maybe I just pick the signature of a private API.
Thanks for your comments and ideas, it helped me to find the source of trouble.