We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Print-Ready File Error
First time using Lulu. Trying to submit my PDF. Size is correct, all fonts are embedded, everything SHOULD work. But it keeps getting to 90% and then sending me the incredibly unhelpful email of "Error Making Your File", which tells me nothing at all about how to get it to work. I've tried it 4 times so far; each failed. Any advice other than "give up and look for a competing service"?