If you want specific help with editing your menu.lst or getting Grub working again, I think it would first help to get a clearer picture of your setup; how about booting your Ubuntu Live CD (the Ubuntu install CD), download the Boot Info Script
to the Live CD desktop, open a terminal (Applications > Accessories > Terminal) and do:
sudo bash ~/Desktop/boot_info_script*.sh
That will create a "RESULTS.txt" file in the same directory from where the script is run, namely your desktop; please copy/paste the contents of the RESULTS.txt file to your next post, highlight the copied text, and click the pound/hash sign "#" graphic button in the forum message box so that the text will get "code" tags put around it. The results of that script will help clarify your setup and hopefully what the best solution to your booting problem might be.