Something that I've encountered when trying to make my multipass is the version of PEtoUSB that I've used. The one listed in the show notes (3.0.0.7) didn't work with my 8Gb Lexar (and I don't think it'll work with anything over 4Gb, but ymmv as always), so I did a google search and found the next version (3.0.0.8) that will work with the 8Gb+ keys.
This newer version also doesn't have the FormatEx error message.