I bought a MacBook Air a week ago. I am connected to the internet and everything is working fine, other than Xfinity streaming and FX Streaming, which uses the Xfinity logon. My PCs work fine on those sites. I have contacted Apple support who advised Xfinity's security certificate is not "handshaking" with my laptop for some reason. I have contacted Comcast multiple times and they are pretty much useless as I keep getting blown off. I run Chrome as the browser, but have tried it with Safari and that does not work either. I have Avast as an anti-virus and have made that an exception. Anyone have any ideas?