I have the same problem and same error message.  I cant use vcenter 5 on vsphere 5 to clone a brand new windows 2008 installation with vmware tools installed.  The Source VM is a pure windows install from the disk, nothing else installed, not even antivirus.  We only purchased vmware (as opposed to use the free version) to get the clone feature, which doesnt seem to work for windows server 2008, unfortunately.