Decided to reinstall my Acer Revo which involves booting from a USB drive as the machine doesn’t have a CD ROM. I was thwarted by an “Unknown keyword in configuration file” error on boot, and this lovely site explained how to fix the problem. 

Credit where credit’s due, but I’ll also repeat the solution as replicating useful information on the Internet is always a good thing.

1. Open the the syslinux folder in the root of the flash drive.
2. Inside is a file called syslinux.cfg you’ll want to edit that.
3. Find the line “ui gfxboot bootlogo” and simply remove the “ui “.
4. Save and try booting again.

Worked perfectly for me, though he also suggests you can get around the problem by typing ‘help’ at the boot prompt and hitting enter a few times. Whichever works for you. I was just pleased to be installing Natty Narwhal on my TV computer :-)