x11-themes/gtk-engines-qtcurve has a USE="firefox3" or USE="mozilla" (depending on the version) flag, which is there to fix problems with Firefox 3 GUI. Since Icecat is just a "GNU-ification" of Firefox, it would make sense to include www-client/icecat to the RDEPEND list. current list: mozilla? ( || ( >=www-client/firefox-3.0 >=www-client/firefox-bin-3.0 ) )" proposed list: mozilla? ( || ( >=www-client/firefox-3.0 >=www-client/firefox-bin-3.0 >=www-client/icecat-3.0 ) )"
Fixed in 1.8.12, just committed to CVS. Thank you!