Web Server and Portal Server have a special upgrade dependency (no bug number)

If Portal Server is deployed to a version of Web Server that you are upgrading to Java ES 5 Update 1, you must also upgrade Portal Server.

Because there is no way on Windows to upgrade Portal Server to Java ES 5 Update 1, you cannot also upgrade Portal Server when upgrading Web Server. Instead, you must migrate Portal Server to useApplication Server as its container before you attempt to upgrade Web Server.