Adding Grub After Ubuntu Installation

The Ubuntu installation isn’t updating the grub configuration file. I updated /boot/grub/menu.lst by hand to use the new kernel. I also installed “Choose next default for grub” and “StartUp-Manager” (System/Administration/StartUp-Manager on the menu).
The StartUp_manager returns the error “Grub configuration file lacks ### END DEBIAN AUTOMAGIC KERNELS LIST”. I exited and backed up /boot/grub/menu.lst, restarted StartUp-Manager, left options alone, and exited. menu.lst was unchanged. Next, I restarted, checked “show text at startup” (you have to change something to get it to rewrite the configuration file) and exited. Still no change.
I’m thinking Ubuntu won’t update Grub’s configuration because I told it not to install a boot loader. These instructions tell how to add Grub after the fact. This is what I did:
$ sudo grub
grub> find /boot/grub/stage1
(hd0,2)
grub setup (hd0,2)
Error 12: Invalid device request

The Grub How-To didn’t provide much help for error 12, other than indicating that you can run update-grub manually:
sudo update-grub
/var/cache/debconf/config.dat is locked by another process

Rebooting solved that problem, but then Grub still refused to install.
As a test, I backed up /boot and installed Ubuntu in another partition and told it to install the boot loader on the /boot partition (as openSUSE was set up). The installation gave me the same error. What’s suddenly wrong with that partition?
Running short on time, I reinstalled and told Ubuntu to format /boot. This worked. I mounted the first Ubuntu partition and updated /boot with the old files to restore the original Ubuntu and the old openSUSE.