VMware has announced that vSphere 5.1 does not support any of the View versions as of yet.

VMware announces on the kb article 2035268 to hold on to the upgrade if your enterprise is using View.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2035268

vSphere 5.1 is not supported with any versions of VMware View

Symptoms

• VMware vSphere 5.1 is not currently supported with any versions of VMware View.

Resolution

Do not upgrade vSphere above the supported versions listed in the VMware View 5.1 Release Notes.

vSphere 5.1 is in the process of being certified against VMware View. To be alerted when this article is updated, click Subscribe to Document in the Actions box.