When GRASS is started from the menu shortcut, there is still an
empty dos CLI in the background.
fwiw there's a bug in the current osgeo4w 6.4.0svn package whereas
that empty DOS box is actually the GRASS terminal prompt but stalled
until the GUI exits. (GUI doesn't background)
see http://trac.osgeo.org/osgeo4w/ticket/83
also note in Colin's stand-alone 6.4.0svn installer the DOS box is now
automatically minimized.
Hamish