troubleshooting multiple inheritance errors

[Jonathan Brandmeyer]

I am attempting to create a class that inherits from a PyGTK class and a
Boost.Python-based class.  When the interpreter executes code like:

class Myclass( gtk.some_class, my_boost_python_class):

I get the exception:
TypeError: multiple bases have instance lay-out conflict

According to the great Google, in most cases that exception was due to a
conflict with multiple base classes defining the member __slots__ at
class scope.  As far as I can tell, neither of the parent classes (or
any of their parents) contains such a member, as evidenced by the fact
that for each parent, class_type.__dict__['__slots__'] produces a
KeyError.

I'm not sure how to continue debugging this problem.  What other kinds
of things can lead to this error?

Thanks for your help,
Jonathan Brandmeyer