Hello:

I've noticed a problem around line 19171 of org.el.  The size of
images is supposed to be controlled by attributes and by
`org-image-actual-width'.  But it seems like the use of `when',
`save-match-data' and `string-to-number' are in the wrong order in
this region, so that `(match-string 1)' is not defined properly when
it's evaluated.  The following instructions should allow you to
reproduce the issue:

Run this:
#+BEGIN_SRC shell
wget http://www.lisperati.com/lisplogo_warning_256.png -O lisp_warning.png
#+END_SRC

Then:
[[elisp:(setq org-image-actual-width '(1200))]]
[[elisp:(org-toggle-inline-images)]]

#+ATTR_ORG: :width 256
[[file:./lisp_warning.png]]

... and the attached patch fixed the problem for me.