Recently I received this error, when I connected to my Virtual Center Server. At first on one ESX-Host, later on on all. I was shure I wouldn´t fix this until I need it. Now I need it urgently andasked troubleshooter #1 – Google. After eliminating any thoughts on serverside issues, I found an entry on Scott Lowe´s Blog. He had exactly the same problem, except he was using 3.0/3.0.2. My setup is running 3.5, with a mix of U-Versions (I know, should be up2date and the same patchlevel on all machines, but anyway…). He mentioned:

Strangely enough, this problem only seemed to affect VI client installations; we were able to connect without any problems from the VirtualCenter server itself.

Hmm… I gave it a try and realized, it was no problem to connect from my VC Server to any machine´s console. That leads me to the point where I realized, it´s a compatibility issue. I´m running VMware Infrastructure Client v2.5.0 Build 204931 on my computer, and VMware Infrastructure Client v2.5.0 Build 227637 on my server. Both connect to VMware Virtual Center v2.5.0 Build 227637.

To make a long story short: avoid differences in Buildnumber can avoid strange behaviour/malfunction. Easy solution for a major problem, but it took me a while to figure it out.