List known build/install problems for OS X.

Doc/whatsnew/3.2.rst

@@ -2443,7 +2443,10 @@ There were a number of other small changes to the C-API.  See the
 :source:`Misc/NEWS` file for a complete list.
 
 Also, there were a number of updates to the OS X build, see
-:source:`Mac/BuildScript/README.txt`.
+:source:`Mac/BuildScript/README.txt` for details.  For users running a 32/64-bit
+build, there is a known problem with the default Tcl/Tk on OS X 10.6.
+Accordingly, we recommend installing an updated alternative such as
+`ActiveState Tcl/Tk 8.5 <http://www.activestate.com/activetcl/downloads>`_ .
 
 Porting to Python 3.2
 =====================