Etch upgrade - /dev/hda1 disappearing.

I recently did a dist-upgrade of my Sarge system to etch. Now, I followed the guidelines in the upgrade suggestions, and did the install of initrd-tools and so on. Still, when I decided to restart, the kernel (2.6.18-4, I believe) gave the following message (after hanging for a minute or so):

ALERT! /dev/hda1 does not exist

And fell to a busybox shell.

If I try and fallback to earlier kernels (.14, .8), it just kernel panics instead saying that it can't find the root partition. I expect that this is probably the same issue, just handled worse? (In fairness, this would happen before with the very old kernels too, so it's possible the problem is different? Of course, now the previous kernel which worked fine before now dies to the kernel panic, while the most recent one installed in the upgrade gives the Alert! error).

I do have an etch install CD handy, and I've booted that into rescue mode. It certainly seems able to at least mount the root partition, as I recognize some stuff in /root. I can also overwrite initrd in / (which is suspiciously small, I'll add- initrd is 4096 bytes? I assume that the real one, initrd.img, is larger, but that's a symbolic link to the boot directory, which wasn't mounted by the rescue shell.)

This problem seems to have occurred before; https://bugs.launchpad.net/ubuntu/+source/initramfs-tools/+bug/32123 for Ubuntu seems to be basically the same issue (makes sense, since Ubuntu is based off Debian).

In any case, does anyone have some ideas? I suppose I could try and stick a new kernel image in, but I wouldn't even know what to change. I'd hope there'd be some kind of simple configuration change to make, but I'm not sure where to start, and I can't seem to cheat my way into my pre-reboot setup from the rescue shell. Worst comes to absolute worst, I suppose I could install a new hard drive, put a fresh install of etch there, then mount the old hard drive as a slave to /oldhd or something (and use chroot). I'd hope that there's a better way around it, though.

Thanks in advance.