Hi again, 
> A bug occurs with org-html-format-latex (in ox-html.el) when called from a non-file buffer. In the context of o-blog, it gets called as (org-html-format-latex "$x$" 'mathjax) but still tries to bind some ltxpng related support. This ends up calling file-name-sans-extension to the output of (file-name-nondirectory (buffer-file-name)) which is nil ...

Cleaner patch uses ignore-errors, that's simpler...

/v