This was reported on r-devel in April for 2.1.0, but isn't fixed in 2.1.1
see
http://tolstoy.newcastle.edu.au/~rking/R/devel/05/04/0586.html
# R --help
[ output omitted, until]
-g, --gui=TYPE Use TYPE as GUI; possible values are 'X11'
(default), 'none', 'Tk' and
'gnome'
solzhenitsyn:~# R --gui=none
ERROR: unknown GUI none
solzhenitsyn:~# R --gui=none
ERROR: unknown GUI none
solzhenitsyn:~# R --gui='none'
ERROR: unknown GUI none
solzhenitsyn:~# R --gui=X11
ERROR: unknown GUI X11
solzhenitsyn:~# R --gui=Tk
ERROR: unknown GUI Tk
solzhenitsyn:~# R --gui='Tk'
ERROR: unknown GUI Tk
solzhenitsyn:~# R --gui='X11'
ERROR: unknown GUI X11
solzhenitsyn:~# R --gui="none"
ERROR: unknown GUI none
--
Robert King, Statistics, School of Mathematical & Physical Sciences,
University of Newcastle, Australia
Room V133 ph +61 2 4921 5548
Robert.King at newcastle.edu.au http://maths.newcastle.edu.au/~rking/
"It might be in the basement,
I'll go upstairs and check .." Escher