Presuming you have updated your Unattend.xmlf were you aware there has been a bug around since MDT 2012 Update 1 with the UDIWizard.wdf file within the MDT Toolkit.......Yes this still exists in MDT 2013 Update 2!
Credit goes Raphael at the The Desktop Team:
http://thedesktopteam.com/raphael/sccm-2012-r2-and-mdt-2013-udi-locale/
I was pulling my hair out a couple of years back with my XP to Win 7 upgrades, fix still stands. Hope this helps.