billboard problems

I have no ideia what i’m doing wrong here, but whatever i do, i cannot make the damn billboards to remain in the same location., when i move the mouse the allways move a bit too.,
take a look at this shots please :

http://www.fysoftware.com/screenshots/p1.jpg
http://www.fysoftware.com/screenshots/p2.jpg
http://www.fysoftware.com/screenshots/p3.jpg
http://www.fysoftware.com/screenshots/p4.jpg

I’m doing the billboards with gl_arb_point_sprite, and here it is the code :

					float quadratic[] =  { 1.0f, 0.0f, 0.01f };
					glPointParameterfvARB( GL_POINT_DISTANCE_ATTENUATION_ARB, quadratic );

					float maxSize = 0.0f;
					glGetFloatv( GL_POINT_SIZE_MAX_ARB, &maxSize );
					glPointSize( maxSize );

					glPointParameterfARB( GL_POINT_FADE_THRESHOLD_SIZE_ARB, 60.0f );

					glPointParameterfARB( GL_POINT_SIZE_MIN_ARB, 1.0f );
					glPointParameterfARB( GL_POINT_SIZE_MAX_ARB, maxSize );

					glTexEnvf( GL_POINT_SPRITE_ARB, GL_COORD_REPLACE_ARB, GL_TRUE );

					glEnable( GL_POINT_SPRITE_ARB );

					glBegin( GL_POINTS );
					{
							glVertex3f( l_p[0], l_p[1], l_p[2] );
					}
					glEnd();

					glDisable( GL_POINT_SPRITE_ARB );

What could be wrong ?
thanks for any help ,

Bruno