Since yesterday, I was defending grub in this forum. I cannot leave you without some words. With lilo or grub, most of the people with multi boot already had this frustration in their lives. I did google for "grub freezes at boot" and between several links, I followed one which is the gnu grub faq: http://www.gnu.org/software/grub/grub-faq.en.htm
If you can't find the problem, I suggest you to show us how did you partition your disk, the size of your hd, the age of your machine, for us to think about it.
I wish you good luck! You will see it's funny.