[R] cycling from x11 window in RCommander to graphics device window: Mac Os 10.6.8

[Simon Kiss]

Dear Colleagues, 
I have recently installed R Commander on my Mac OS 10.6.8. I'd like to use it for an undergraduate class this year.
Everything appears to be working fine, except for one thing.  I cannot use Command-tab to cycle from the X11 window in which RCommander is running to any other window open in my workspace.  This is particularly important because I cannot cycle to the graphics device window that is opened when I call a new plot.  If I force quit the X11 window and Rcommander, R remains running and I can see the graphics device window and the plot looks fine.
But as you can imagine, this is quite laborious, having to restart.
I've looked through the help documentation and tried reinstalling tcltk prior to opening up Rcommander, but that does not address the problem.
Any thoughts?
Yours, Simon Kiss
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Simon J. Kiss, PhD
Assistant Professor, Wilfrid Laurier University
73 George Street
Brantford, Ontario, Canada
N3T 2C9
Cell: +1 905 746 7606