I used the tutorials on pendrivelinux with a tutorial on the ubuntu wiki pages to get a live CD and  a usb stick working together.

Because I cannot boot from USB sticks on the different pcs I am frequenting.

The point is, I am not a linux expert. I tried to use that tutorial only because it easily explained to me at  that time how to format my USB stick.

I inserted then the Live CD, inserted the USB stick, switched the PC, pushed F6 on boot and wrote persistent at the prompt.
Then it was possible for me to use the feisty fawn live cd with persistent mode.

I checked that feisty fawn works with persistent mode but hardy does not work so I used feisty and did not follow the instructions on changing the initrd.

Then I discovered the filed bug, tried to change the initrd and failed.

I hope this helps.