Comment 5 for bug 923070

fstab still supports disk-ids, but I guess that's not part of grub, really, it's to mount the fs.
In grub.cfg and other grub files you are correct it has UUID. But let's put aside UUIDs for a moment, cuz that did not change anything for the blank screen.

I have tested all what you mentioned before opening the ticket.

Let me recap for easier reading:

How am I doing the copy?
Byte-per-byte.
At the interface level I use 2 different ways:

1- I use g4l bootable CD and image my root partition in RAW mode (http://sourceforge.net/projects/g4l/)
2- If I am inside the distro on one disk and the other disk's partition is unmounted, I use the following command:

sudo dd if=/dev/sdxy ibs=4096 conv=noerror | gzip -9 > /img/filename.img.gz

Never had a problem with either ways, except now with Kubuntu 11.10 (never tested with older versions of *buntu).

Now if I clone my root partition (and I also clone the /tmp partition), remove the original disk and try to boot with only the cloned disk plugged in like you mention, I still get the blank screen instead of grub2's menu. That is my problem, actually and the reason why I opened this ticket.
I have tested these exact steps using grub-legacy as well and surprisingly I get the same result. Which complicated furthermore my troubleshooting and testing as now I have no idea what else to test.

So the cleanly installed Kubuntu with either grub2 or grub-legacy can boot up no problem. I then initiate an image and restores the image to another identical disk and whether that cloned disk is booted alone or with the original disk as SATA1 (SATA0 being the cloned disk), I get the same blank screen instead of grub's menu.

That is 4 different setups:

1- grub2, cloned disk as SATA0 and original as SATA1;
2- grub2, cloned disk alone as SATA0, original disk completely unplugged;
3- grub-legacy, cloned disk as SATA0 and original as SATA1;
4- grub-legacy, cloned disk alone as SATA0, original disk completely unplugged.

Result: exact same. Blank screen with top left blinking cursor and only command working is CTRL-ALT-DEL.

Cloning is performed either of the following ways:

1- Using g4l bootable CD and image my root partition in RAW mode;
2- If I am inside the distro on one disk and the other disk's partition is unmounted, I use sudo dd if=/dev/sdxy ibs=4096 conv=noerror | gzip -9 > /img/filename.img.gz