The Grub menu entries look normal, other than your 10.04 installation still uses Grub legacy.
At the Grub menu, try to manually boot 10.04 and let us know where it fails.
Press 'c' to get to the grub prompt
ls (hd1,5)/ # Does it find 'vmlinuz' and 'initrd.img'
linux (hd1,5)/vmlinuz root=/dev/sdb5 ro
If that doesn't work try these for the kernel and image lines:
Added: These commands really don't do anything differently than the menuentry as far as loading the kernel and initrd image. It does eliminate some of the other commands built into the menuentry. I'm not confident it will work but it's worth trying and perhaps any error messages will shed more light on what's going wrong.
linux (hd1,5)/boot/vmlinuz-2.6.32-41-generic root=/dev/sdb5 ro
If you can boot into 10.04, I'd recommend purging 'grub' (Grub) and installing 'grub-pc' (Grub 2). The instructions can be found by going to the Grub2 Ubuntu community doc: