i just had a customer change the flavor of a cake that I had already baked and crumb coated with buttercream frosting.  Can I freeze this cake with the icing on it or is it a loss?

Yes, you can freeze it.  But you should charge her full cost for the layer baked and already  iced,  plus the new flavor she changed to.

Thanks for your reply!!  Definitely charging for it!!   What is the best way to freeze it?  Wrap in saran wrap and freezer bag?

I just use a layer of saran wrap a plastic bag or a rubbermaid type box, depending on the size.