JJ,

Last time I encountered similar problem, where some of the
external resources are not included when saving the page, is
when I have an addon for saving web pages as MHTML. i.e.
the addon somehow interfere Firefox's built in functionality for
saving web pages using "Web Page, complete" option.

Sounded reasonable. So, I disabled all four of them (with the possible
culprit being RequestPolicy). Alas, I got the same result: The webpage with
the two images and the CSS page referenced from it, and nothing more.

Funny though, as I can see the background images, and can save them by
right-clicking on them too.

Regards,
Rudy Wieser