I put wterm -sh -bg blue -fg white -ls -sl 9999 +sb -vb -tr -cr red -fn '-*-fixed-*-*-normal-*-9-*-*-*-*-*-*-*' into /usr/share/xfwm4/themes/default.keys/keythemerc and it won't execute, nor will ' replaced with "'s.
xfwm4 is really not a "general purpose" app launcher. The line in the rc file is limited to 80 chars and your command is truncated (ie, it's not related to quotes) Why not using xfterm4, and set TERMCMD to your "wterm -sh -bg blue -fg white -ls -sl 9999 +sb -vb -tr -cr red -fn '-*-fixed-*-*-normal-*-9-*-*-*-*-*-*-*'", that'll do the job. BTW I've increased this limit to 255 chars in CVS HEAD; it doesn't hurt either. Cheers, Olivier.