Executing debug-enabled code hangs

[<Ken.Williams@thomsonreuters.com>]

Hi,

I use org-mode a lot with "BEGIN_SRC R" sections that I execute manually
with C-c C-c in an *R* session buffer.  Sometimes I go to that session
buffer and execute some code manually, and occasionally I turn on
debugging for a function with "debug(func)".

If I then go back to my org-mode buffer and execute that function again,
Emacs hangs.  I can't get back to the *R* session in order to step through
the function or disable debugging, so I have to force-quit Emacs.  I know,
I should remember to turn off debugging for those functions, but sometimes
I forget, and the consequence is that I lose the whole session.

Known problem?

This is on:

 * OS X 10.6.6
 * Aquamacs 2.2, which is based on GNU Emacs 23.3.1
 * Org-mode 7.5
 * ess version 5.13

I do have a big huge thread stack trace that Aquamacs generated, if that
would be helpful.

Thanks.

--
Ken Williams
Senior Research Scientist
Thomson Reuters
http://labs.thomsonreuters.com