This is not OpenDNS bug actually.If your ISP is assigning you dynamic IP and assume that IP you were assigned for current session was earlier assigned to another OpenDNS customer and this customer (likely to be some company) has opted for blocking microsoft.com in their OpenDNS preference.Since OpenDNS doesnt know that IP is now assigned to other person i.e you, the same policy still applies on that IPTo avoid this either create OpenDNS account with Dynamic IP updater OR disconnect and reconnect (so u get new IP)