Since I had a stable triple boot with Leopard for over a year, I assume my difficulties stem from upgrading to Snow Leopard. My original system for installing the Leopard Triple Boot fails with Snow Leopard, so I’ve searched for a new one. The only one on the ‘net is here. I’m suspicious, since 1) they list Snow Leopard second, as if it is simply the same as Leopard and might well be untested, and 2) my attempts to make their system work have all ended in failure.
I’m certainly learning a lot about MBR and GUID partition schemes, but none of it is getting me where I need to be. More updates when I’m less frustrated.