I've been using CS3 for about 6 months now, and I'm not sure what you're referring to. Could you screencap or give a bit more details? It might be something that occured from transferring your project from 6.0 to CS3, because I don't think I've come across Frame Blend so far (though admittedly, my CS3 is installed in french because my computer is set to french default, so I might know the term as something else. Doesn't sound a familiar bell though).