Just for the record, replying to myself concerning the complete lockup of
Firefox and Epiphany when started under Gnome 2.18:

I found out it has to do with dbus-launch. When running Gnome, or a
different window-manager, without it, then the browsers work flawlessly.

Because I realized that without dbus-launch the "theme" in Gnome is lost, I
experimented with different themes, and by using "Glider" instead of
"Clearlooks" I was finally successful. Firefox no longer freezes!

So changing the theme seems to be a workaround, but there is a problem
somewhere (fonts?) !

-- 
    _  Frank Wille (frank@phoenix.owl.de)
 _ //  http://sun.hasenbraten.de/~frank/
 \X/   Phx @ #AmigaGer