A colleague of mine was attempting to build an ISO of a Windows 7 image from our MDT share and ran into a problem. No matter what computer he tried to build the ISO media 
As it turns out, the root cause was a corrupt driver file in the Out-Of-Box Drivers folder in the MDT share. Deleting the driver resolved the issue.
Take a look at the following link on Microsoft’s MDT forums for details on how to troubleshoot this problem, as well as how to fix it:
http://social.technet.microsoft.com/Forums/en/mdt/thread/ecd1e59f-7c1e-432c-8759-8fc65eb036d1
-Joe