[C++-sig] ‘Base’ is an inaccessible base of ‘Derived’ ??

[Anders Wallin]

Hi all,
I'm trying to expose a base-class with pure virtual functions, and a
derived class. Following the example here:
http://www.boost.org/doc/libs/1_42_0/libs/python/doc/tutorial/doc/html/python/exposing.html#python.class_virtual_functions

both in my real code, and in a minimal test-case, I get a long list of
errors which ends with:
/usr/include/boost/python/object/inheritance.hpp:99: error: ‘Base’ is
an inaccessible base of ‘Derived’

my minimal test-case is here:
http://pastebin.ca/1839949

This is on stock-standard Ubuntu, i.e. boost 1.38.0, g++ 4,4,1, and python 2.6.4

any ideas what is going on? is there working code for the
tutorial-documentation somewhere?

thanks,

AW