In case anyone else ran into this... I spend a day or two debugging a non-booting machine, only to find out that the tools in initrd (FC3, x86-64) only support 16 raid devices. Since the vg with root included md16 and higher, I couldn't boot. Root is now on its own raid0 (md5) to keep initrd happy. Yes, I'm planning on upgrading, but before this change I couldn't get the fc6 disks to recognize my pre-existing installation, so I couldn't just upgrade.
