Do you have svg enabled? You can check the value of the pref svg.enabled on the about:config page. See http://kb.mozillazine.org/about%3Aconfig

Note that the svg.enabled pref is not used in FF4, since SVG support is hardcoded on. https://bugzilla.mozilla.org/show_bug.cgi?id=617448

For what it's worth, after '''FF 4.01''' couldn't open an SVG file I tried '''Chrome 11.0.696.60 unknown''' and it had the same problem with the same file: [http://upload.wikimedia.org/wikipedia/commons/6/6c/Map_of_New_Mexico_highlighting_Lincoln_County.svg Lincoln Co NM @ Wikipedia] Also, if you scroll the window, you can see that SOMETHING is rendering, just not what you would expect: [http://en.wikipedia.org/wiki/File:Map_of_New_Mexico_highlighting_Lincoln_County.svg PNG preview of SVG @ Wikipedia]