Hi, Henri-Paul.  Please allow me to suggest that you consider using "Easy Templates" to insert your source-code blocks:

    http://orgmode.org/org.html#Easy-Templates

Using the template:

    <s <TAB>

is not only faster than typing:

    #+begin_src

    #+end_src

it also inserts both the begin and end statements simultaneously, thus lessening the chance of a mismatch.

-- Mike
From: Henri-Paul Indiogine <hindiogine@gmail.com>
To: emacs-org <emacs-orgmode@gnu.org>
Sent: Tuesday, September 27, 2011 2:17 PM
Subject: [O] Error on LaTeX export

I would like to thank you for helping me out with this LaTeX export
problem.  The enter debugging on error setting was very helpful.  I
had a missing #+end_src statement.  I have many, many blocks of code
in a long document, thus it was easy to miss and difficult to find.

Love org-mode!

Henri-Paul

--
Henri-Paul Indiogine

Curriculum & Instruction
Texas A&M University
TutorFind Learning Centre

Email: hindiogine@gmail.com
Skype: hindiogine
Website: http://people.cehd.tamu.edu/~sindiogine