[CentOS] migrating files for centos virtualization, virtual disk no longer boots.

All,

I am playing with virtualization on centos 5.
I took my old redhat 7 disks and created a 10GIG virtual disk, I 
installed redhat 7.
Now I am trying to get the EXACT image copied off of my actual redhat 7 disk
so that I know it is the same (including all patches, updates and OTHER 
things I did to it that I
have forgotten about).

I booted the redhat 7 image just fine at this point. I also copied it 
for backup so I dont have to install again.

So on my centos 5 box I mounted the image with a loop command.
mount -t ext3 -o loop,offset=32256 redhat7.img /mnt/image
This works fine.

Then I logged into the redhat 7 system and executed the command
tar --exclude ./proc --exclude ./mnt --exclude ./sys --exclude ./dev 
-cvf - . | ssh root at 192.168.1.8 "( cd /mnt/image ; tar xvpf -)"

Where 192.168.1.8 is my centos 5 box and /mnt/image the mounted image.

The copy seems to go fine. But after I do this when I try to virtualize 
the redhat7 image it stops at:
GRUB

When I copy the second image back on top of the first image it then 
boots again. So glad I made that copy
of the image file.

What is happening with the tar command that is messing up grub and 
keeping it from booting?

Thanks,

Jerry