recent kernels won't boot

[Evan Martin]

On 10/4/05, Art Alexion <art.alexion at verizon.net> wrote:
> Kernel updates execute the update-grub process.  The /boot/grub/menu.lst
> file works with single (#) and double (##) comments.  when booting grub
> ignores text following both single and double comments, but update-grub
> only ignores double comments.  It updates your grub menu to reflect
> kernel updates using the lines following single comments.
>
> If you added or removed drives or partitions, your /boot directory which
> used to reside on /dev/hda2, may now reside elsewhere, but the single
> commented defaults in menu.lst still point to /dev/hda2.
>
> I suggest you have a look and if this is your problem, make the changes
> to the defaults manually, and then run update-grub.

Thanks for the suggestion!  But I haven't changed any hardware.
I have both the working and nonworking kernels installed, too, so
update-grub hasn't been involved.  It's as simple as: if I pick 
2.6.10-5-686-smp from the boot menu it boots fine, but if I pick
2.6.12-6-686-smp from the boot menu it fails.