[ESS] Interactive SAS mode hangs

[Sparapani, Rodney]

> I'm not sure what the distinction you're drawing (setup vs ESS itself) means for me in practice. What types
> of things should I be looking at in my setup to explore reasons for the failure of M-x SAS? What does M-x SAS
> depend on that ess-sas-interactive doesn't?
 
Well, if you know that ess-sas-interactive works, then there should be
nothing stopping M-x SAS from working.  But, now you would have to do
some debugging of the ESS elisp code to actually figure out what is
wrong.  Is it a bug in your setup?  Such as emacs 23.1 is buggy.  Or
is it a bug in ESS itself?  It's hard to say at this point.

> Also, a colleague drew my attention to the *Messages* buffer so I thought I'd try your first suggestion
> again (emacs -q, manually load ESS after setting a debug flag) and look there for error messages. I found one:
> QuitError during redisplay (void-function with-silent-modifications)

Probably due to emacs 23.1 not having this function.  You might be
able to grab the function from the emacs 24 source.  emacs 23.1 is
from 2009 and many of us have moved on to newer, less-buggy versions.
It might be better if you used an ESS version that was more concurrent 
with emacs 23.1 like ESS 12.09 from Sep. 2012.