Unfortunately, Microsoft has misconfigured a security feature (OCSP stapling) on their servers which got now cached in your local Firefox installation. In order to resolve that, please enter '''about:config''' into the Firefox address bar (confirm the info message in case it shows up) and search for the preference named '''security.ssl.enable_ocsp_stapling'''. Double-click it and change its value to '''false''' - this will degrade a security feature in Firefox, so please revisit it in a couple of days again after Microsoft has fixed their stuff and turn it back on again then.