You used Deja Vu to make a backup ("clone") of your entire startup disk, but you are unable to boot from the backup disk.
Be aware that not all FireWire drives support booting OS X. See this article:
Getting the boot, FireWire edition
For this reason, Apple does not officially support booting OS X from FireWire drives.
If it doesn't work (even when you have followed the recommended procedure), your drive may be the problem. Try installing OS X on it the traditional way and see if it boots.