I upgraded our vcenter last time in September 2014 so the "old" version could be the "vCenter Server 5.5 Update 1c for Windows | 22 JUL 2014 | Build 1945274". Now we are on the latest version "vCenter Server 5.5 Update 2b | 09 OCT 2014 | Build 2183111". But I think the reconnect of the hosts after upgrading der vcenter solved the problem not just the upgrade.
