[racket-dev] known problem?

In DrRacket 5.1 on Windows 7, hitting Alt-Space reproducibly produces
this output:

system-menu in frame%: unimplemented; args were '()

 === context ===
C:\Program Files
(x86)\Racket\5.1\collects\racket\private\more-scheme.rkt:265:2:
call-with-exception-handler
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\mrtop.rkt:179:27:
on-subwindow-char method in frame%
C:\Program Files
(x86)\Racket\5.1\collects\racket\private\more-scheme.rkt:149:2:
call-with-break-parameterization
C:\Program Files
(x86)\Racket\5.1\collects\racket\private\more-scheme.rkt:265:2:
call-with-exception-handler
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
C:\Program Files
(x86)\Racket\5.1\collects\mred\private\wx\win32\window.rkt:705:2:
call-pre-on-char method in window%
...