Have you tried booting with a LiveCD/install CD and attempting to access your files that way? One way to do this would be with the Gentoo one. After booting it up, try a command like this to mount the drive:
mount /dev/xvda2 /mnt/gentoo
If that succeeds, look at its contents to make sure they're right:
If they are, then assign an IP and default route (using information from the "IP List" page in your control panel):
ifconfig eth0 your.assigned.ip.address your.assigned.net.mask
ip route add default via your.assigned.gateway.ip
echo "nameserver 184.108.40.206" > /etc/resolv.conf
If the response to the second line was "command not found", try this alternate one:
route add default gw your.assigned.gateway.ip eth0
Then, assign a password:
And start SSHD:
Finally, connect with your favorite SCP client (I use WinSCP), navigate to /mnt/gentoo, and copy off the files that you need to back up.
In terms of fixing your Ubuntu boot problem, a quick Googling turned this up, which may help: http://askubuntu.com/questions/125428/g ... lling-1204
. Note that, before typing the commands they give, you will likely need to assign your IP as you did with Gentoo.