They are both VC Update 2. I tried doing a repair of Update Manager but it is failing. I'm working with support to try to resolve this & will post result if I get it fixed.
"Installer (build 104263) which includes vCenter Server 2.5 (build 104215) and its subcomponents (including VMware vCenter Update Manager (build 63972), VMware vCenter Converter (build 62397), VMware Infrastructure Client software, VMware License Server, and VMware Infrastructure WebAccess)."
I've just removed & re-installed Update Manager with Update 2. Didn't have time to wait for support.