You have to run mc in a term, like an rxvt or xterm.
Glad to be here for my first post.
How do you launch midnight commander (mc) from the icewm toolbar?
This line does not seem to work:
prog "MC" "/blah-blah/blah-blah-blah/mc.xpm" mc
So, prog MC [icon] rxvt -e mc
The icon is the second entry, the executable is the third.