In an earlier post I mentioned that vSphere 5.1 is not compatible with any versions of VMware View. Well I am please to you inform you all that today VMware have released an express patch for ESXi (ESXi510-201210001) which fixes an issue that caused the incompatibility issue. 

The official VMware KB with details on how to get this latest patch can be found here: http://kb.vmware.com/kb/2035268