Hi Rainer,

I am aware of this problem, and although I don't know any a good
solution, I do have a good workaround (example attached [1]).

The problem is that org-latex removes all of the #+ lines from the
beginning of any Org-mode file which has headlines as part of the export
process.  This means that by the time it's Babel's turn to run code
blocks, the #+BABEL line has been removed, and the session is not set.
If there are no headlines, then this problem does not arise.

I sent in a patch last week, [2] but it's application would have broken
other features of the latex export, I've yet to work out a good solution
to this.

There is a decent work-around.  Whenever there are no headlines, then
the #+BABEL: line works fine on LaTeX export, when there are headlines,
then header arguments can be placed as properties in the headlines to
the same effect.

Cheers -- Eric

Rainer M Krug <r.m.krug@gmail.com> writes:

> Hi
>
> I have the attached org file.
>
> It seems that when exporting to a pdf, the :session argument is ignored, as
> I get a
> Org-Babel Error Output buffer with:
> Error: object 'x' not found
> Execution halted
>
> and an Org-Babel Error buffer with the same text, and the resulting pdf does
> only show the code..
>
> HTML export, works as expected.
>
> If I put :session *R_test* behind #+begin_src (R2.org) it works.
>
> Cheers,
>
> Rainer

Footnotes: 
[1]