With kernel-2.6.23-0.149.rc4.fc8 and three IDE devices (two drives, one DVD-RW drive), the kernel suddenly can't see my primary master and therefore refuses to boot because it can't find my root partition. When I fall back to booting from kernel-2.6.23-0.142.rc3.git10.fc8 and make no other changes, everything works just fine.
Is there any way you can capture the boot messages with serial console or netconsole? Or try a later boot disk, -rc5 at least?
This is no longer an issue in 2.6.23-0.164.rc5.fc8.