When you run LANG=C some-program & in xfrun, it opens the webbrowser with three tabs: http://www.lang=c.com/, http://www.some-program.com/ and http://www.&.com/ instead of executing the actual command. Even escaping the command as "LANG=C some-program &" doesn't work, in this case a blank firefox window is opened. $ rpm -q xfce-utils xfce-utils-4.8.1-2.fc15.x86_64
Exporting variables like this are not support at all.