Welp, broke my computer again, sort of.
See, I've confirmed that the instability I've been experiencing with the ol' OSX boot is definitely due to booting it from GRUB; it works fine from EFI.
So I decided I'd give Chameleon another shot -- maybe another bootloader would be more stable? Worth a try, right?
'Cept I can't get Chameleon to work this time, and it fucked GRUB up so it won't boot anymore either. (Edit to add: Apparently an MBR disk can't have more than one bootable partition? Guess it's been awhile since I took that A+ test. So okay, it's easy enough to get GRUB working again, but it doesn't help me get Chameleon working.)
The good news is that Chameleon boots just fine from CD, so I can still boot OpenSUSE that way.
The bad news is that, for some damn reason, holding down "C" to boot from CD doesn't work anymore on my Mac, so I've had to stick the damn helper card back in to access the boot menu by holding down Option when I power up.
(The other bad news is that AVG Free decided to flag fucking rundll32.exe as a virus and delete it, but Win8 must have restored it automatically because it worked okay on a reboot. But that's all the Win8 I did today.)
Anyway. Hoping I can get this damn mess fixed tomorrow. Because I've got better shit to do than keep fucking around with bootloaders.