I have a ESXi 4.1 server (free one) setup with some virtual machines. On my XP laptop I have vCenter converter standalone 4.3 and vSphere 4.1 client installed and everything was working find. Now I setup a ESXi 5.0 serve (free one). I can't use converter standalone 4.3 with the ESXi 5.0 so I uninstall the 4.3 and install the converter standalone 5.0. I was able to use the converter to create a VM on the ESXi 5.0 using a VM on the ESXi 4.1 as the source. So far so good. Now the vSphere 4.1 client on my laptop is not able to work with the ESXi 5.0 so I uninstall it and install the vSphere client 5.0. The problem I have is that the vSphere client 5.0 won't connect to either the ESXi 4.1 or the ESXi 5.0 server. The error I get is complaining about the SSL certificate. If I uninstall the vSphere client 5.0 and re-install the vSphere client 4.1 I can connect to the ESXi 4.1 server. When I get the pop up complaining about the certificate I can hit the ignore button. I didn't get that option with the vSphere client 5.0.