After installing some updates, I rebooted my machine, and it hung after printing the word "GRUB". I tried rerunning the installer and having it reinstall the boot loader, and that just made it print "GRUB " over and over in an infinite loop. I tried using the "rescue system" mode, and running grub-install and the kernel postinst script by hand, but that didn't help either. grub-0.97-34.fc10.i386 kernel-2.6.27-0.398.rc9.fc10.i686 I'm not sure what other packages are relevant...
a second manual grub-install seems to have fixed it. (maybe i typoed the first time). I'm still not sure why it stopped working in the first place. It definitely booted successfully immediately after the F10 upgrade, so something happened to it after that point
Thanks for the update. Please reopen this bug if it happens again.