I'm using 3.6.7 and latest wordpress version, and have a problem with this different look between browsers.
http://i51.tinypic.com/241vadi.png
This is normal look on Chrome, Opera, and even IE9.
But this is what shows for Firefox 4.
http://i51.tinypic.com/zl24p5.png
Currently using W3 Total Cache and Yoast SEO.