At Fri, 16 Sep 2011 10:50:01 -0700 (PDT),
Michael Hannon wrote:
> Greetings.  I've been having problems lately in exporting Org-Mode source-code
> documents to HTML and/or PDF.
> 
> I'm running Org-Mode 7.7 with Emacs 23 on 64-bit linux (Fedora 15).
> 
> I've appended a document that exhibits at least some of the problem.  The
> problems are similar to the problem described at:
> 
>     http://comments.gmane.org/gmane.emacs.orgmode/45316
> 
> and can *sometimes* be circumvented by executing org-reload.
> 
> In the particular example shown below, the HTML export works as expected, but
> the PDF export fails with message:
> 
>     org-export-latex-preprocess: Wrong type argument: stringp, nil
> 
> By the way, everything worked fine in the example until I added the last
> source block:
> 
>     #+begin_src R
> 
>       x
> 
>     #+end_src
> 
> I tried using what I take to be the latest version of Org-Mode:
> 
>     Org-mode version 7.7 (release_7.7.290.g65d05)
> 
> but that only made things worse.  I tried an HTML export with this version, and
> it generated a horrendous-looking message that begins with:
> 
> org-babel-R-evaluate: Wrong number of arguments: #[(session body result-type
> result-params column-names-p row-names-p) Æ=}...
> 
> followed by a bunch of stuff containing enough non-printing characters that
> it's hard to reproduce in email, and ending with:
> 
> ...org-mode/lisp/ob-R.elc" . 9734)], 5
> 
> I'd welcome any help/advice that anybody can provide.


Could I ask you to provide the entire backtrace for both errors?

M-x toggle-debug-on-error RET

The backtrace might contain information about the exact place where a
string is expected. If you can't copy it into the email program save
to disk + gzip + attach should do the trick.

Best,
  -- David
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