I did a bit of Googling about and came across the following link from VMware, unfortunately this did not solve my problems as I had actually not integrated vCenter with Active Directory yet. I was still using Administrator@vSphere.local for day to day admin tasks.
The next step was to try the vSphere Web Client, I was faced with the following error from it "Client is not authenticated to VMware Invetory Service - https://labvc.company.com:10443 Unable to create the managed object for - urn:vmomi:AuthorizationManager.AuthorizationManager:"
My next thought was to try and integrate vCenter to Active Directory to give a kind of workaround, I clicked on the Single Sign On\Users and Groups pane of the Web Client and it threw the " 'alias' value should not be empty" error again.
As it was clearly related SSO and the Inventory Service, I did some research on the Log Files for these components, do a search on your vCenter Server for the "ssoAdminServer" log file.
Yet again another unhelpful error in the logfile, it then got me thinking that it could be a DNS issue as the vSphere Web Client stated it could not authenticated to the Inventory Service via it's FQDN.
It tried an "nslookup" on the vCenter Server to see the status of DNS. It could not resolve the primary DNS server.
I resolved the DNS server issue and tested so that name resolution was working correctly. Following this I then rebooted the vCenter Server to refresh all of the services.
Once it rebooted and all of the vCenter services had time to start I tried again and it resolved the issue. It also seemed like a good time to integrate my vCenter with Active Directory.