I reported this to emacs (bug 18095):
http://lists.gnu.org/archive/html/bug-gnu-emacs/2014-07/msg00736.html

It's still happening with latest emacs and org-mode


On Wed, Jul 2, 2014 at 11:51 PM, Daniel Clemente <n142857@gmail.com> wrote:

> Since this org-babel + tramp-cache incompatibility is very puzzling, I
> continued researching it. The line that makes my Python block stop working
> (i.e. outputting None instead of the "x" I asked with print "x') is this
> one, found in tramp-cache.el:
>
> (add-hook 'kill-buffer-hook 'tramp-flush-file-function)
>
> Its code is:
>
> (defun tramp-flush-file-function ()
>  "Flush all Tramp cache properties from `buffer-file-name'.
> This is suppressed for temporary buffers."
>  (unless (string-match "^ \\*temp\\*" (or (buffer-name) ""))
>    (let ((bfn (if (stringp (buffer-file-name))
>   (buffer-file-name)
> default-directory)))
>      (when (tramp-tramp-file-p bfn)
> (with-parsed-tramp-file-name bfn nil
>  (tramp-flush-file-property v localname))))))
>
>
> That "temporary buffer detector" is working correctly because org-babel
> buffers have names like " *temp*-993012", which are correctly detected.
> I'm afraid that the (string-match ...) will forget the last search, so later
> (match-string) done by babel will be from the wrong search. Can this happen?
>
> --
> Daniel
>
>
> On Fri, Jun 27, 2014 at 4:50 PM, Daniel Clemente <n142857@gmail.com>
> wrote:
>
>> I confirm that with Debian's Emacs, org-babel works well after the
>> (require 'tramp-cache):
>> GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.12.2) of 2014-06-06
>> on barber, modified by Debian
>>
>> But it fails with my compiled one from 2014-06-20.
>>
>> So is it because of tramp-cache or org-babel?
>>
>>
>> On Fri, Jun 27, 2014 at 12:19 AM, Daniel Clemente <n142857@gmail.com>
>> wrote:
>>
>>>
>>> El Thu, 26 Jun 2014 12:36:47 -0400 Eric Schulte va escriure:
>>> > > #+BEGIN_SRC python :results output
>>> > > print "x"
>>> > > #+END_SRC
>>> > >
>>> > > It prints:
>>> > >
>>> > > #+RESULTS:
>>> > > : None
>>> > >
>>> > > I expected to see "x". This worked some days ago.
>>> > >
>>> >
>>> > This works for me using the latest version of Org-mode with an Emacs
>>> > launched by running "make vanilla" from the base of the Org-mode repo.
>>> >
>>>   I didn't know "make vanilla". It worked fine from there, I don't know
>>> why from "emacs -Q" it didn't.
>>>
>>> > Maybe the problem is in your configuration?
>>>
>>>   Exactly, it is from my configuration, because after loading my full
>>> configuration, I see the problem again and code highlighting suddenly
>>> disappears.
>>>
>>>   I identified the exact lines that cause org-babel to stop failing.
>>> Bewonder:
>>>
>>>   (autoload 'tramp "tramp" "Remotely access files." t)
>>>   (require 'tramp-cache)
>>>
>>>   Yes! After C-x C-e on the first line, org-babel still works. After C-x
>>> C-e on the second line, it doesn't work anymore.
>>>   There were some Tramp changes in latest Emacs, maybe they are bad. I'm
>>> using:  GNU Emacs 24.4.50.1 (x86_64-unknown-linux-gnu, X toolkit, Xaw
>>> scroll bars) of 2014-06-20 on la4
>>>
>>>
>>>   What a strange bug...
>>>
>>>
>>
>