Swap used to be /dev/sda6. So you changed the order of the partitions, and so the names have changed.

You can enter the grub shell and use tab completion to locate which partition has the /boot partition or directory. You just need to enter 3 lines. One for the kernel. One for the initrd file and then the command "boot".
Start with "kernel (hd0," and press tab. You will get a list of your partitions. You want either (hd0,5)/ or (hd0,6)/. Using tab completion you don't need to know the exact version of the kernel by heart.

After booting up (hopefully), you will need to edit your /boot/grub/menu.lst and /etc/fstab file. In the menu.lst file correct the references to the effected partitions. Grub uses a notation like (hd0,4) which is equivalent to /dev/sda5. Don't forget to correct the resume= entry in the kernel boot options. This is the "kernel" line in /etc/grub/menu.lst. It should refer to your swap partition which is /dev/sda8. Don't use the grub device notation for it, because it is a kernel boot option and not a grub value.

After saving your edits, run "sudo /sbin/grub-install /dev/sda".