In case you guys land into an issue when you have decomissioned your old linked vcenter or migrated to a new one but when you login using the vpshere client you get the below message.
It means that you have a stale entry in the ADAM database and here is how you can fix it. (Be careful what you do in here!)
Open up ADSI EDIT, right click and select "Connect to"
In the following dialog box click "Select or type a distiniguished or Naming Context" and type dc=virtualcenter,dc=vmware,dc=int
Then in the below section select the option under Computer as seen below,and here type the name of your working vcenter in which you are receiving the pop up box and then after you have filled in the information click OK.
After you have connected to your vcenter server context, drill down to OU=Instances as you can see below and right click on each of the instances below and look at the vmw-vc-URL and vmw-vc-InstanceName value and if you see your old vcenter name in them which you have decommiomsed or un-linked, this is the intance you have to delete. So go ahead and delete it. After this restart your vsphere client and login again and now you will no longer see the message.