Non-member operator overloading, linker complains

Why does the following code (stripped down to the bare minimum) not
build?

To be specific, it gives me a linker error like this:
error LNK2019: unresolved external symbol "class Matrix<double,3,3>
__cdecl operator-(class Matrix<double,3,3> const &)"
(??G@YA?AV?$Matrix@N$02$02@@ABV0@@Z) referenced in function _main

The problem seems to be the need to access private members in the
overloaded operator definition and the subsequent friend declaration in
the class. Forward declaring the function outside the class does not
change anything.

Compiler is VC++ 8.0 EE.
To my surprise, it did and does work using VC++ 7.0.

What is the issue and how can I resolve it? Slightly puzzled over this
seemingly simple problem...

Thanks,

Michael

-----------------

#include <iostream>
#include <algorithm>
#include <vector>

template<typename T, unsigned int d, unsigned int e> class Matrix
{
private:
    friend Matrix<T, d, e> operator-( const Matrix<T, d, e>& m );

    typedef std::vector<T> data_type;
    data_type data_;

public:
    Matrix( T value )
    {
        data_.resize( d * e );
        std::fill( data_.begin(), data_.end(), value );
    }

    // ...
};

template <typename T, unsigned int d, unsigned int e>
Matrix<T, d, e> operator-( const Matrix<T, d, e>& m )
{
    Matrix<T, d, e> mRes( m );
    Matrix<T, d, e>::data_type::iterator itrEnd = mRes.data_.end();
    for ( Matrix<T, d, e>::data_type::iterator itr =
          mRes.data_.begin(); itr != itrEnd; ++itr )
        (*itr) = -(*itr);
    return mRes;
}

template <typename T, unsigned int d, unsigned int e, unsigned int f>
Matrix<T, d, f> operator*( const Matrix<T, d, e>& m1,
                            const Matrix<T, e, f>& m2 )
{
    // does multiplication without accessing
    // private members of Matrix<>
    // ...
    return Matrix<T, d, f>( 0.0 ); // dummy return
}

int main()
{
    Matrix<double, 3, 3> m( 1.0 );
    Matrix<double, 3, 3> n( 2.0 );
    Matrix<double, 3, 3> o = m * n; // no problems
    Matrix<double, 3, 3> p = -n; // yields linker error
    return ( EXIT_SUCCESS );
}

-----------------

      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]