Okay, more info:
When I add the old IOPCIFamily.kext from 10.4.4, add the revised IOPCCardFamily.kext, repair permissions and so on, and restart, this is what I get. It all goes smoothly until:
IOPCCard info: Intel PCIC probe: TI xx12 rev 00
USBF: 51. 92 EHCI controller unable to take control from BIOS
USBF: 51. 94 AppleUSBEHCI[0x2de6800]: unable to obtain ownership: 0xe00002be
USBF: 51. 97 AppleUSBEHCI[0x2de6800] : : UIMInitialize - Error Occurred (0xe00002be)
USBF: 51.101 AppleUSBEHCI: unable to initialize UIM
After that, I get the grey block and it just hangs.
When booting normally (that is, without the old IOPCIFamily.kext from 10.4.4 but with the revised IOPCCardFamily.kext), I get this:
USBF: 38. 71 EHCI controller unable to take control from BIOS
USBF: 38. 73 AppleUSBEHCI[0x2090000]: unable to obtain ownership: 0xe00002be
USBF: 38. 75 AppleUSBEHCI[0x2090000] : : UIMInitialize - Error Occurred (0xe00002be)
USBF: 38. 78 AppleUSBEHCI: unable to initialize UIM
A couple of reboots convinced me that the numbers, "38 .71" and so on, don't mean anything. What's interesting is the one major change - it's 0x2090000 instead of 0x2de6800. I have no idea how to use this information , though. Anyone more skilled than me willing to interpret?
BTW, I figured out how to get MacDrive working. The main issue is that the MacOSX drive wasn't showing up in Windows Explorer even with "View Mac Disks" checked in the MacDrive options and a drive letter assigned. I noticed that it was showing up when I would go to save a file, though. This got me thinking that maybe it would show up if I used Windows Explorer alternative. To that end, I picked up this awesome bit of freeware called A34
and voila, there the drive was. No more clean installs (for now)! The only minor issue now is that I have to change the MacOSX drive letter in Acronis every time I reboot Windows. But that's a small price to pay.