A picture is worth a thousand words... so does anyone know how to fix this font blurriness in Firefox?

(You'll need to right-click the picture below go to View Image to view it full-size; it's too small to see anything here.)

Note: My other applications (and the Firefox non-client area, as you can see in the screen) are completely fine, so obviously going to System->Appearance and changing the font settings isn't fixing the situation.

Edit:

Not letting web pages to use their own fonts also doesn't help:

See how the upper one is still sharper?

Also, Firefox's own menu bar doesn't render the same way as the page content (menu bar below, page content above). They're both Segoe UI: