When you using vSphere 4 and and using MDT 2012 update1 with Windows Assessment and Deployment Kit you run in de following error. Same thing wil also with Workstation 8.
Solution 1: Do not install Windows Assessment and Deployment Kit on your MDT Server. You can still using MDT 2012 Update 1 with waik 3.5 if not deploying Windows 8 or Windows 2012 right now.
Solution 2: Upgrading you vSphere server to the latest version (5.1) or Upgrade Workstation to latest version (Version 9).
Michael Niehaus created a troubleshooting guide about MDT
Check out: Troubleshooting Windows Deployments 2012-09-11.pdf
MDT 2012 Update 1 no longer uses SETUP.EXE to install Windows 7 and above. One side effect of this is that $OEM$ folders are no longer going to be copied, since that was something that SETUP.EXE did that the MDT LTIApply.wsf script doesn’t handle.
I’ve never been a big fan of using the $OEM$ folder structure, as it’s just as easy to add explicit XCOPY steps into the task sequence. But for those of you out there that are using them, you can leverage the attached script (CopyOEM.zip) in your task sequence to do that.
To set this up, first copy the script into your deployment share. Then, add a new step to the task sequence right after the “Install Operating System” step to run the script. It should look like this:
Now, it will follow the original MDT logic for locating the appropriate $OEM$ folder to use, checking in this order:
where %DeployRoot% is the path to the deployment share, %TaskSequenceID% is the ID of the running task sequence (e.g. WIN8), %SourcePath% is the path within the deployment share for the operating system being used, and %Architecture% is either X86 or X64, depending on the boot image being used.
Once it finds a folder, it will look for two folders in that $OEM$ folder and copy them to the appropriate place for the new OS:
The script doesn’t deal with any other folders because it’s too messy to do that from within Windows PE – drive letters aren’t the same as what they would end up being in the full OS
Download: CopyOEM.zip
Source: Copying $OEM$ files and folders with MDT 2012 Update 1
When you configure MDT you could specify an organization name To specify these, you can configure them in CustomSettings.ini:
_SMSTSOrgName=WardVissers
_SMSTSPackageName=My Package Name
That’s great if you want to hard-code the values, but what I wanted was that _SMSTSPackageName is set to the name of the task sequence that is being executed. That’s a little harder to do, because the task sequence hasn’t yet been selected when CustomSettings.ini is being processed, and you can’t set these read-only variables once the task sequence has started.
So this is one of those cases where you have to modify one of the MDT scripts, in this case LiteTouch.wsf. Fortunately, it’s a really trivial change. Look for this line:
oEnvironment.Item("_SMSTSPackageName") = "Lite Touch Installation"
And change it like so:
oEnvironment.Item("_SMSTSPackageName") = oEnvironment.Item("TaskSequenceName")
That line is only executed if _SMSTSPackageName is blank after CustomSettings.ini has been processed, so it won’t have any effect if you manually configured a value in CustomSettings.ini.
With that change, you can now see the name of the currently-running task sequence: 
You can download the file here: LiteTouch.7z (Tested with MDT 2012 Update 1)