In the case that you did not back up your menu.lst from your ubuntu installation, you can allways use the following bootable CD to restore the MBR and create the missing entrys on GRUB:
Super Grub disk Live CD * The Use * Repair Grub * Restore MBR back to Windows Super Grub Disk is used to repair Grub and the MBR and reinstall on another partition. It can also restore the original MBR uninstalling Grub for users wishing to leave GNU/Linux, without risk of making the computer unusable after formatting the Linux partition. You can download Super Grub Disk at this address: http://download.linux-live-cd.org/Super_Grub_Disk/download/binaries/sgd/cdrom/ -- This message posted from opensolaris.org