preupgrade F15 fails

[sean darcy]

I ran preupgrade-cli on F14 x86-64. Everything seemed to work.

grub.conf:

title Upgrade to Fedora 15 (Lovelock)
	kernel /upgrade/vmlinuz preupgrade repo=hd::/var/cache/yum/preupgrade 
ks=hd:UUID=78716504-df9a-43a7-9a1c-d37c87ec1fbd:/upgrade/ks.cfg
	initrd /upgrade/initrd.img

and the UUID points to /boot

But on reboot, there's a long (1-2 minute) blank screen, followed by a 
black and white checkerboard.

This box has:
AMD Phenom(tm) II X6 1055T Processor.
01:00.0 VGA compatible controller: nVidia Corporation NV43 [GeForce 
6600] (rev a2)

Not very exotic.

Is this supposed to work?

sean