I now have a suitable workaround: save the K5 player as a multi, and then unload it. Figuring out how to do this was a vexation, however, because of a quirk in K5 (sounds like a mountain in the Himalayas). I always move the player away from its default position over on the left, to a right of center position. However, doing this obscures the little message box that comes up when you do the save/unload thing. So I couldn't figure out why K5 was not responding - it was waiting for a response from me. I finally realized there had to be a box lurking behind K5, and indeed that was the case. So finally then I was able to save my work, after 20 or so attempts. I'll have to let them know at NI about this, I would think it would be easy to fix. However, the overall problem remains, I can't save my work in sonar with CS2 on the K5 player, without doing the workaround. Can't figure out if this is a sonar or NI problem, but I would think a fair number of folks must encounter it.
BTW, the idea for the workaround came from another Sonar thread, by stlum, from 4/20/09 - thanks, you helped me a lot!