Abstract Interface - Assertion Error

["Mike.McNett" <michael.mcnett@usma.edu>]

I am having a problem with creating one Interface, then an Abstract
type that implements that interface, and a concrete type from the
Abstract one.  When I don't use the interface, all is good.  When the
Abstract type is based on the Interface Type, however, I get a
"System.Assertions.Assert_Failur" runtime exception.  Here's the basic
code:

In Graph_Interface package, I define Type Graph_Interface_Type is
Interface;

In Abstract_Graph package, I define Type Abstract_Graph_Type is
ABSTRACT NEW Graph_Interface.Graph_Interface_Type with Private;

In my Matrix_Graph package, I define Type Matrix_Graph_Type is new
Abstract_Graph_Type With Private;

Using the above, everything compiles but I get the assertion error.
When I change the Abstract_Graph_Type so that it is just Abstract and
doesn't implement the interface, all is good.

Any ideas / thoughts?

Thanks,
Mike