Last night on my rawhide laptop I installed

kernel 3.7.0-0.rc6.git4.1.fc19.

Upon reboot I got a grub shell prompt. Turns out my /boot was empty.

I've been installing and using pretty much every recent kernel, including the nodebug ones. I notice that I also installed a newer version of dracut a couple of days ago. I'm pretty sure I've installed and run several kernels since the newer dracut, so I'm not sure it is the problem.

For the record, my workaround was

Boot an F17 resuce disk
chroot /mnt/sysimage
Insert a slightly old F18 disk (that didn't have rescue mode)
rpm --oldpackage of the kernel and dracut off the F18 disk
reboot

darrell