There seems to be a bug in org-mode 8.2.5g for tangling source blocks.

If I have an org-file with just this in it:

#+BEGIN_SRC python :tangle test2.py

a = 1

print a*2

#+END_SRC

#+RESULTS:
: 2

And  then I run org-babel-tangle, I get this error:

byte-code: Before first headline at position 3 in buffer test.org<2>

The file tangles fine with an older org7.9 version. It also tangles fine if
I add a headline above the source block.

The error seems to come from this line:
             (org-back-to-heading t)  ; Sets match data

L476 in ob-tangle.el

John

-----------------------------------
John Kitchin
Associate Professor
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
http://kitchingroup.cheme.cmu.edu