Hi--

I did a "clean" install of elpa package

  org-plus-contrib-20121224

(i.e. removed old package, restarted emacs with -q flag, installed above
package, restarted emacs again...)

Then I started gnus, started composing a message, and executed the command

  M-x org-mime-htmlize

The result is the following error:

  org-export-as-html: Wrong type argument: stringp, t

Here is the backtrace: