We've been having problems deploying Windows Server 2008 R2 virtual machines from templates using the VMware vCenter and it's built in guest customization.

It appears that there may be an issue either with Microsoft's built-in sysprep utility in 2008 R2, or with VMware's vCenter guest customization wizard when using a Key Management Server, or KMS. A KMS is part of Microsoft's Volume Activation 2.0 as described here - http://www.microsoft.com/licensing/existing-customers/product-activation... and in this TechNet article - http://technet.microsoft.com/en-us/library/bb892849.aspx