Today, I ran into an interesting problem using VirtualCenter's Clone to New Machine which integrates sysprep functionality.
Apparently, Guest Customization of Windows 2008 is not supported at this time (5/8/2008). Luckily, I found excellent solutions on the VMTN Forums.
If you switch the template's OS specification to VISTA, you are able to proceed with your clone.
This change to the version allows the Customization Wizard to continue.