>
>> I do not know where to search for the reason, these variables work for
>> Eric but not for me (and John...).
>
> I don't think they work for Eric if he tries to set them as file variable.
>

This was my fault.  I miss-interpreted what was happening on my system,
these aren't working for me either.

>
>> So attached is a simple patch (search-and-replace) that renames all
>> org-babel-default-header-args:* variables to
>> org-babel-default-header-args-*
>
> In keeping with the spirit of the original naming I'd suggest
> switching from ":" to "/".  I still think this is a bug in how Emacs
> evaluates the local variables, but since it has been that way for ages
> it probably has become a feature.
>

I agree that this is an Emacs bug.  The attached patch fixes this bug, I
suppose it should be submitted to the emacs-dev mailing list.