pickle error - 'module' object has no attribute '_reconstruct'

[Skip Montanaro]

Saw a new-to-me error today when trying to unpickle a moderately large
object (about 500k):

    AttributeError: 'module' object has no attribute '_reconstruct'

Google turned up nothing as far as I could tell, "_reconstruct"
doesn't appear in the docs and pickletools.dis() was happy to 
disassemble the pickle.  This was with Python 2.4.  Any ideas about
the cause of this error?

Thx,

Skip Montanaro