Whenever there's a kernel update on my system, the new kernel packages are installed, and the grub.conf file does not get updated. Which is THE WAY I want it to be. I never did like the way grub.conf got updated behind my back, so to speak, after a kernel update.
Now I don't need to worry about a new kernel busting anything, as the previous working kernel will be booted, even after a kernel update.
I haven't followed this thread too closely, but if you set UPDATEDEFAULT=no in /etc/sysconfig/kernel .. the new kernel will be installed, grub will be modified, but the default line which is used to choose the default kernel will *NOT* be updated.
Barry