ISSUE: When navigating to your vCenter Web Client (Flash) page, the browser no longer allows you to check the “Use Windows session authentication” box.
FIX: need to navigate to https://vmware-plugin:8094 and Advanced and then Proceed.
Note: For this who are interested, the reason your machine is able to resolve https://vmware-plugin is because during the installation of the plugin your hosts file is manipulated to point vmware-plugin to 127.0.0.1