Problem with cPickle and cElementTree

[Barry]

I recently tried switching from ElementTree to cElementTree.  My
application parses a collection of large XML files and creates indexes
based on certain attributes.  This entire collection is saved as an
instance of my Database class.  Using ElementTree and cPickle has
allowed me to save these instances and use them later.

Using cElementTree significantly reduces parse time (~50%) and memory
~(15%) but cPickle refuses to pickle the database object.  I receive:

TypeError: expecting string or Unicode object, NoneType found

The offending line of code simple shows my invocation of cPickle,
which is not helpful.

Doing exactly the same thing with ElementTree works fine.

It appears that the objects returned by cElementTree do not pickle
correctly.  Is this a know issue?  I was unable to find any reports of
this problem.

Any info would be appreciated!

Barry