A possible solution might be to try and reinstall Grub by booting into live. Boot into live, open a terminal, run "sudo fdisk -l" and find out on which partition you installed Ubuntu. It will be something like /dev/sda5. Mount that partition somewhere. You can do this by "mount /dev/sda5 /mnt" and run the following command to install/reinstall grub.
sudo grub-install --root-directory=/mnt/ /dev/sda (Note: It might not be sda. That depends on your hard disk's name which will be shown by "sudo fdisk -l").
Try restarting after this and hopefully it will work. :)
Or, you can boot into live and mount the partition in which you have data on and copy that data from there too.
You might want to refer to http://sosaysharis.wordpress.com/2011/06/29/recovering-grub-after-installing-windows-using-ubuntu/