I have a home server running Fedora 12 and decided to upgrade to Fedora 14. I ran through the upgrade process using preupgrade with instructions from here. I ran into an issue withi insufficient space n my /boot partition and followed the instructions from the troubleshooting section that allows the upgrade to download img files during the upgrade. The last I saw my machine, it was happily downloading the img file.
When I cam back a few hours later, I have a system that will no longer boot. I'm not a complete n00b, so I downloaded and booted from sysrescueCD.
It appears the /boot partition is still in place, and still has the Fedora 12 kernels; the grub menu.lst appears coherent (I've not looked at one before as I've used Slackware & lilo mostly).
Seems like trying to reload the MBR might make sense, but I'm at a loss as to how to troubleshoot and procede.