I have noticed the same problem in Mozilla Firefox V 3.6.12. The field is not shadowed, the displayed text is written in black color.
On the opposite, the same page is shown correctly on Internet Explorer V 8.0.6001.18928. - the input field is shadowed and gray color is used for the input fields text.
The web application is made in Seam framework V 2.2.1CR2 and RichFaces implementation V 3.3.3.CR1
Is there any workaround to get properly skinning in Firefox for this case?
check custom styles applied using firebug. if you generated project with seam-gen it's adds some default stylesheets which causes some such effects as I saw earlier.
Working fine for me at richfaces-demo environment with 3.3.3 Final.