I used Win7SP1_5in1-x86-Aug2015-en-US.iso.
I followed Method 3 (boot.wim image #2) and used the modified Auto.cmd with the menu.
I added a AutoUnattend7.xml file which was the same as \_ISO\WINDOWS\WIN7\Sample.xml but had a Win7 Pro product key
This worked as expected just fine.
Either you corrupted the boot.wim or your xml file is causing the problem.
P.S. I used the MPI_FAT32 shortcut.
Subject Re: Re: Re: Re: Re: Automating Windows Install from .imgPTN