Calling virtual method of base class nested in template class (VC++ 6.0)

Hi all.

Here's a little quandry I've run in to and can't tell if it's a compiler
bug, or if it's bad code. First, here's the code:

===================================
#include <stdio.h>

template < typename T >
class B
{

public:

  B( ) { }

  class N1
  {

  public:

    N1( ) { };

    class N2
    {

    public:

      N2( ) { };

      virtual void f( )
      {
        printf( " B< >::N1::N2::f( )\n" );
      }

    };

  };

  T _m;

};

class D : public B< int >
{

public:

  class N1 : public B< int >::N1
  {

  public:

    N1( ) : B< int >::N1( ) { };

    class N2 : public B< int >::N1::N2
    {

    public:

      N2( ) : B< int >::N1::N2( ) { };

      virtual void f( )
      {
        typedef B< int >::N1::N2 Bint; // must do this to avoid VC6.0's
"error C2352: 'B<int>::N1::N2::f' : illegal call of non-static member
function" bug.

        printf( " D::N1::N2::f( )\n" );

        // B< int >::N1::N2::f( ) causes the compiler to complain (see
typedef above). However, VC7.1 works fine.
        Bint::f( );
      }

    };

  };

};

void
main( int argc, char* argv[ ] )
{
  D::N1::N2 n2;

  n2.f( );
}

==================================

Invoking n2.f( ) causes an infinite loop, dumping out "D::N1::N2::f( )"
ad-nausium. I am trying to call the base-class f( ) in B::N1::N2, but the
VC6.0
compiler just generates code that instead calls D::N1::N2::f( ) recursively.

VC7.1 compiles this just fine (even on the commented out line).

What am I doning wrong? Or, is this a compiler bug?
If it's a bug, is there a fix or how can I call the base's f( )?

BTW: I'm stuck w/VC6.0, so please don't suggest using VC7.1; thanks.

Thanks for any help you can offer!

- Roger