The vSphere Clients, prior to the Update 1 release, cannot be used to access the vCenter Server or ESX hosts. A Microsoft update that targets the .NET Framework, released on June 9th 2010 is causing this issue. The update http://support.microsoft.com/kb/980773 causes the vSphere Client to stop working.
To correct the issue there are two options that can be performed:
- Download and install the latest version of the vSphere Client. To download the latest version, visit our website at http://downloads.vmware.com/d/info/datacenter_downloads/vmware_vsphere_4/4.
- Remove the MS update from your Windows operating system. The vSphere Client works after the update is removed.