Try nerfing the local source declaration in your @font-face
directives.
There's a known bug in either Firefox or the Google Font API that prevents the variants of fonts to be used if the font is installed locally, and matches the defined local name:
http://code.google.com/p/googlefontdirectory/issues/detail?id=13
To effectively nerf the local declaration, just make your local source string some nonsense. The generally accepted convention for this is to use a the smiley unicode character ("?"
). Why? Paul Irish has a great explanation up on his blog: