Since IDLE and the turtle modules both use Tkinter and thus are both Tcl/Tk applications, it wouldn't be surprising if you had problems trying to run a program using the IDLE module from within IDLE.  However, I find I can successfully run at least one of the supplied Turtle demos from IDLE 2.7.1 and IDLE 2.6:

  cd /Applications/Python 2.7/Extras/Demo/turtle
  idle2.7 tdemo_paint.py # or idle2.6

and with either of the two IDLE variants (32-bit -> Tk 8.4, 64-/32-bit -> Tk 8.5).  Can you supply a simple script to demonstrate the problem you see?

Keep in mind that, at the moment, neither of the standard python.org 2.7.1 installers support using ActiveState Tk 8.5.9.  The 32-bit-only installer will use ActiveState Tk 8.4, if installed, otherwise use the Apple-supplied Tk 8.4.19(?) in 10.6.  Python 2.7.1 was released before a 64-bit capable version of ActiveState Tk 8.5 was available so, as released, it will only link to the Apple-supplied Cocoa Tk 8.5.7 in 10.6 and that version has proven to be very unreliable when used with IDLE.  You should be able to build from source a Python 2.7.1 that will link to ActiveState 8.5.9 if it is present during the build but beware that there are a number of issues both major and minor that have been recently fixed in Python (and are in the current release-2.7 maintenance branch that should appear as a 2.7.2 release in the future) as well as a few issues in Cocoa Tk itself which should be fixed in an upcoming release of ActiveState Tk 8.5.