Comment 9 for bug 231075

I found out another detail:
  update-initramfs -u -k 2.6.24-19-server
will work without an error message; it is
  update-initramfs -u -k 2.6.15-52-server
that will fail with the udev hook script message. So the udev message is just misleading about which kernel it is talking about (kernel being updated instead of running kernel).

So I suggest changing the message
  udev hook script requires at least kernel version 2.6.17
to
  udev hook script cannot process kernels before version 2.6.17

What remains to be checked is whether the boot machinery is in a usable state in the current situation. If yes, the error can be downgraded to a warning, and a message as in
  The kernel was not changed and should still be usable
could be issued.
If no, the message should be
  The kernel is not bootable anymore. However, a new kernel is being installed and *should* be bootable. You can uninstall the old kernel(s).