If you are using MDT Update 1 to deploy Windows 7 SP1 language packs then please pay attention, this post will save you time.
MDT 2010 Update 1 does not address the Enhanced Language Pack handling in Windows 7 SP1. This means that if you add a Windows 7 SP1 language pack to the workbench it will not appear in the task sequence wizard.
Thankfully the solution is fairly simple. You simply update the language handling function in the DeployWiz_Initialization.vbs script.
For details of the updates on how to make this update please see - http://support.microsoft.com/kb/2547191
This post was contributed by Ben Hunter, an Architect with Microsoft Services