$ /opt/python2.4/bin/python
Python 2.4a1+ (#1, Jul 30 2004, 20:22:17) 
[GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin
Type "help", "copyright", "credits" or "license" for more 
information.
>>> from Carbon.CF import *
>>> c = CFArrayCreateMutable(0)
>>> isinstance(c, CFMutableArrayRef)
True
>>> del c

The interpreter hangs after deleting c. This also happens when the 
call to isinstance is left out.