If your vCenter Server login domain user account is associated with a large number of domain groups and multiple domains are configured as SSO identity sources, then you might not be able to logon to vCenter Server via the vSphere Web Client/vSphere Client after upgrade.
For more information check out this VMware Knowledge Base.
The release of vCenter Server 5.1 Update 1a will resolve the issue.
ReplyDeletehttps://www.vmware.com/support/vsphere5/doc/vsphere-vcenter-server-51u1a-release-notes.html#resolvedissuesvcenter