When using cPickle to pickle / unpickle an object instance whose
__dict__ contains a dictionary of NumPy Arrays (on a windows32 system),
some of the array elements have the wrong type raising a ValueError:
could not convert string to float.  

On UNIX platform this error does not occur, and the data is read out in
the correct type every time.  
Forcing the caller to use pickle.py module instead removed the issue.

Statements about the imprecision of cPickle (such as issue1536, 655802),
or its deprecaition (now I can't find where that was mentioned), would
assist.  By contrast the current state of the documentation implies that
cPickle is better overall, and thus should be used preferentially.