For what it's worth, I was able to reproduce the behavior you describe (also on OS X 10.7 using Python 3.3 and the latest ActiveState Tcl/Tk 8.5.11).  Scrolling is a lower level GUI operation that, AFAIK, managed by Tk and OS X frameworks, and not by Python or Tkinter, so my guess is that the problem you're seeing would need to be addressed there.  Unless someone else has a better suggestion, I would advise asking about this on the Tkinter-discuss mailing list (http://mail.python.org/mailman/listinfo/tkinter-discuss) and/or, possibly even better, on the Tcl Mac mailing list (http://dir.gmane.org/gmane.comp.lang.tcl.mac) particularly if you can demonstrate the problem with a Tcl code segment.  Please report back any updates you receive.  Good luck!