JFTR I had a similar problem a few days ago. I'm using uxrvt instead of gnome-terminal. Here is the relevant modified line in .emacs:

    (format "urxvt -e bash -c \'%s %s\'"

I had to call bash before calling mutt-open, but I think this might be

something urxvt-specific.

The relevant note: The "sleep 0.1" hack of mutt-open didn't work for me in urxvt. I had to use an ugly "read" in order for mutt to receive the push commands.

Just my two cents.