According to Sean A. Walberg:

Just a short note from Fedora Core 1 on a box that was previously RH 9. Upgrade steps are simple -- no CDs necessary, no reboots needed other than to bring up your new kernel.

Install Yum. Edit /etc/yum.conf to point to a Fedora mirror (use Gilbert's patches, but change $releasever to 1) Run "yum upgrade" Reboot into your new kernel

That's a bit of a stretch. I had to delete one rpm that was causing a dependency failure, but it wasn't necessary anyway.

Lemme guess... The "galeon" package was the culprit? I ran into the same problem after upgrading (from CD) from RH 9 to Fedora Core 1, not as a result of the upgrade itself, but when I subsequently used yum to load the updates to Core 1. Running "rpm -e galeon" was all it took to eliminate the dependency loop.

I also had to edit /boot/grub/grub.conf to default to the new kernel (not sure if that was the upgrade that defaulted it to the old one).

That's odd, since yum normally takes care of updating grub.conf to default to the new kernel. I think it runs some sort of test first, to decide if changing the default is "safe", and that may have failed in this case, due to significant differences between the kernels.

And, more strangely, my eth0 didn't work even though it was detected (wouldn't receive packets even though they were being sent). eth1 worked fine, though. I noticed Fedora has some hardware management stuff that comes up on boot, this behaviour is classic interrupt stomping.

That's even odder, and I wonder if it had anything to do with yum. You might have encountered the same issues if you had upgraded via CD.