Boot Camp in Yosemite can't see Macintosh HD

I have a 27" Late 2012 iMac with a 1TB Fusion drive running Yosemite 10.10.1 and Boot Camp with Windows 7 (which I just installed). My previous Boot Camp installations were all able to see the Macintosh HD from Windows 7 using the Boot Camp HFS+ driver (installed with the Support Software package). This installation cannot.

I thought that maybe I didn't have the HFS+ driver installed correctly, but lo-and-behold, it is: I can see and read external HFS+ drives just fine. It's only the internal drive that I can't read. Windows Disk Management can see that the drive exists but the OS simply can't read it in Explorer.

Could this have something to do with it being a Fusion drive in Yosemite? I've read some comments that may allude to this (though very sketchy and I don't want to put ideas into your head--I need to know the real reason). I'm 99.9% positive that I had Boot Camp on this computer a few months ago and it read the Macintosh HD just fine, though I could be thinking of my previous (Mid 2010) iMac; I can't be sure.

Please help. This is driving me crazy.

Thanks so much!