[racket] Beginner can't get some Macintosh command keys to work

I've just resumed my efforts to learn scheme after a long hiatus, and I
can't seem to get to first base:
I'm using Racket 5.2 with Macintosh Lion software (version 10.7.2).

Many of the command keys don't seem to work.  Specifically Cmd-R prints an
r in whatever window I'm in, rather than running.  CMD-N (new) and CMD-T
(new tab) do not work, even though selecting from the menu gets me a new
window or a new tab.  Some command keys work - The preferences come up
with CMD-, Paste works with CMD-V, and save works with CMD-S.  I haven't
tested everything.

Is this a new bug, or do I have my head screwed on the wrong way or Š

TIA for any and all help.

Leonard