What I've done:

1. Created 1 GB partition (ext4)
2. Installed to USB using unetbootin
3. Added a second partition as described in your guide

Won't boot. All I get is "Missing operating system" when I try to boot off the USB drive. Checked fdisk, partition is flagged bootable. Mounted the partition, files are there. I'm perplexed. Thoughts?

Thanks.