Microsoft Update Kills vSphere Client

Got a problem running vSphere Client today? Seeing the following pop-up when trying to access your VMware stack?

Login doesn't really continue, but in fact, ends with the following error:

Your environment has not been hacked! It's a problem with your most recent Windows Update, introducing a .NET exception that your "old" version of VMware vSphere Client can't handle. While you can uninstall the offending patch(es) to resolve the problem, the best remedy is to login to VMware's site and download the latest vSphere Client (VMware KB 1022611).

By the way, if you're vSphere Client is old enough to be affected (prior to Update 1), you might need to scan your vSphere environment for updates too. If you have SnS, run over to VMware's download page for vSphere and get the updated packages, starting with the vSphere Client: you can find the installable Client package with the vCenter Server Update 2 downloads.