Unable to download MKS plug-in in Firefox 4.0 and 5.0 (2004238)
The Lab Manger server must have a built-in object certificate to successfully download the VMware Remote MKS plug-in in Firefox 4.0 and 5.0. You must ensure that the SSL certificate is from a trusted certificate authority. If you do not install an SSL certificate, VMware generates one. However, this certificate prevents Firefox from downloading the MKS plug-in from the Lab Manager server.
Configure the vCenter Lab Manger server with an SSL certificate from a trusted certificate authority. To know more about how to configure a server certificate, see http://technet.microsoft.com/en-us/library/dd441360(office.13).aspx and http://support.microsoft.com/kb/816794.