I just ran into a really distressing problem with Mac OS X. I mounted my Panther-PowerBook's boot drive on my Jaguar-PowerMac, so that I could copy the PowerBook's copy of SubEthaEdit from its Applications folder into my PowerMac's Applications folder.

SubEthaEdit wouldn't run on Jaguar. Okay, maybe it was built against the newer SDK, so it won't run. Same thing happened when I tried SubEthaEdit 1.1.4 from the disk image on Jaguar.

A little later, I accidentally launched iTunes. It presented me with its license agreement and setup windows! Weird, I thought, I guess my iTunes setup was wrecked somehow.

Then a few minutes ago I tried double-clicking on a PDF (I'm still using the Jaguar-PowerMac at this point) that's in my ~/Documents folder. A window appears saying it can't run the application because it's not compatible with the system!

I right-click the PDF, choose Open With, and there's two Preview entries listed. 2.0.1, and 2.1 (default). 2.1 is the version on Panther!

So, because I had my Panther machine mounted, it was loading THOSE applications, because their version numbers were higher!

That's BAD.