Installing new kernel freezes upgrade

I'm running ubuntu 12.04 on my Imac and It was working fine for a while.

Today I did a upgrade and now it's been stuck for about one hour on

Generating grub.cfg
Found linux image: /boot/vmlinuz-3.2.0-24-generic
Found initrd image: /boot/initrd.img-3.2.0-24
Found linux image: /boot/vmlinuz-3.2.0-20-generic
Found initrd image: /boot/initrd.img-3.2.0-20
Found memtest86+ image: /boot/memtest86+.bin

I don't know what is safe to do because one hour I don't think anything will change...

Thanks for reading.