Welcome to Mint Mintnewbie
Frankly I don't understand.....
When you boot from a CD you never get to grub, I suppose you mean the boot menu of the Live CD
it says "Kernel missing". It doesn't even reach the grub. Then I can write commands from "root:".
Could you describe what you do and the error messages you get because this makes no sense. You can end up in a "busy box" with both Cassandra/Celena and Feisty - is that it?
As always - check the md5sum (the command is md5sum) and burn at the slowest speed possible