This is just a case of bad timing.
Back in August, BlueCoat implemented some changes to the BlueCoat WebFilter. It introduced some new categories and renamed some other categories. On the ProxySG, no change was necessary for the renamed categories. However for ProxyClient (the client side install that provides protection when off the corporate network), you needed to manually update the config.
Unfortunately for us, no one bothered to update that config. While reviewing some BlueCoat best practices, I doublechecked our existing settings and found that we still had the old categories selected in ProxyClient. I made the required changes and saved to server. On my client, ran the updater and got an error back, “Received status 400 from server”. I received the same error testing directly from my browser.
Opening a case with support they directed me to a Technical Alert – ProxyClient Installation is Failing with HTTP 400 response from server. I’d seen that before running into this problem, but hadn’t read it since I wasn’t installing ProxyClient. Didn’t remember the error 400 tiein. It turns out, the problem occurs when making the SSL connection from the client to the server to pick up the configuration. This is true of a new install or an updated configuration.
The cause of the problem is MS12-006. Since this contains SSL fixes for the BEAST vulnerability, I’m going to have to ignore BlueCoat’s suggested workaround of uninstalling the Microsoft security update. Not sure if this can be fixed with a new ProxyClient version or if I’ll be waiting for a ProxySG release which would involve much more testing.