C2236: unexpected 'class'

[glsl09]

i have one header file Matrix4x4.h . it includes another header files. when i compile the code. it gives error "C2236: unexpected 'class' 'Matrix3x3'. Did you forget a ';'? " where i made mistake. how can i fix the problem. thanks in advance

#ifndef matrix4x4
#define matrix4x4

#include "Vector2D.h"
#include "Vector3D.h"
#include "Vector4D.h"
#include "Matrix3x3.h"

class Matrix3x3;     // compiler shows here error C2236

class Matrix4x4
{
public:
        ..................................
        ..................................
	Matrix4x4& operator=(const Matrix4x4& matrix1);
	Matrix4x4& operator=(const Matrix3x3& matrix1);
	friend Matrix4x4 operator-(const Matrix4x4& matrix1, const Matrix4x4& matrix2);
	friend Matrix4x4 operator+(const Matrix4x4& matrix1, const Matrix4x4& matrix2);
	friend Matrix4x4 operator*(const Matrix4x4& matrix1, const Matrix4x4& matrix2);
	friend Matrix4x4 operator*(const Matrix4x4& matrix1, const Matrix3x3& matrix2);
	friend Vector4D operator*(const Matrix4x4& matrix1, const Vector4D& v);
	friend Vector3D operator*(const Matrix4x4& matrix1, const Vector3D& v);
	friend Vector2D operator*(const Matrix4x4& matrix1, const Vector2D& v);
	friend Vector4D operator*(const Vector4D& v, const Matrix4x4& matrix1);
	friend Vector3D operator*(const Vector3D& v, const Matrix4x4& matrix1);
	friend Vector2D operator*(const Vector2D& v, const Matrix4x4& matrix1);
	friend Matrix4x4 operator*(float t, const Matrix4x4& matrix1);
	friend Matrix4x4 operator*(const Matrix4x4& matrix1, float t);
public:
	float m[16];
};

#endif