We just setup a new vcenter appliance and added the VMware vCenter Server 5 Standard license. Everything OK.
We added 2 of our 3 ESXi host machines to the vCenter using our VMware vSphere with Operations Management Standard licenses with 6 processors (each ESXi has 2 processors).
We cannot add one of three ESXi hosts. It always returns an error "A specified parameter was not correct licensekey"
The host is running ESXi 5.1.0 build 799733
Thanks