I'm kind of in the same boat ... I cannot for the life of me get Tails running via USB on my Macbook Air. I've read all the documentation and the clearnet threads - seems it's a common problem that some people are able to get around, but others aren't. Booting from a CD/DVD works just fine, and I'm able to create the USB (it even shows up in the reFIT/reFIND menu at startup) but when I boot it, it gives me an error. This is so frustrating.