During the new installation of VMware vCenter 5.5, I received an error 26002 while it was trying to register with Inventory Service. The solution was pretty simple, thank you the article that I found here: http://www.petenetlive.com/KB/Article/0000941.htm. Even thought I copied the SSL folder from the previous version of vCenter (as the upgrade document says), it did not work. Actually, the SSL folder should be copied from C:\Program Data\VMware\Infrastructure\Inventory Service to C:\Program Data\VMware\VMware Virtual Center before vCenter installation. So, you need to create the C:\Program Data\VMware\VMware Virtual Center folder first.