To find out what is wrong, starts from the default package.Then add your applications or your drivers one by one and use "Create new Target Image and ISO", postconfig script in Finals folder.
Okay if your source is clean and you use a unchanged Win7PE_SE_2013-??-??.zip project,there are two things left that could be a problem.1. if you have an Anti virus program running during build, please disable it while you build the PE.2. thought unlikely, but possible it's a driver related issue,so please create the build with all Drivers scripts disabled.To do this simply remove the check box on Drivers in the main tree.
it's untouched, there's a program that automatically downloads it, I think it's win builder, winpe builder
I've moved all the files to another machine and did the same process, with the same ISO. It worked flawlessly.