Hi, I posted something about this a few weeks ago, but got distracted before I had a chance to look into it further ... Revisions 1.5 and up of activeattr.py in the MA package cause a fatal error when pickling is attempted. The pickle and cPickle modules don't allow unbound instance methods to be pickled and the ActiveAttributes mixin is storing attribute handlers, such as ActiveAttribute.basic_get, as unbound instance methods. Revision 1.4 works fine if basic_get is modified so that an AttributeError is raised instead of a KeyError when an attribute is not found. This bug was introduced in an attempt to allow child classes of MA to be able to modify activeattributes. I suggest reverting back to rev 1.4 of activeattr with a modified basic_get method and forgetting about allowing child classes to do this. Cheers Tavis