I've noticed that Exchange autodiscover is not working for me while setting up a tablet. I believe it used to, and I suspect the problem may be that exchange.businessclass.comcast.net is using a certificate which expired 7/29/2013. On a PC, it's simple to ignore the cert error, but this can be more challenging on a mobile device.
Either that or my cname isn't pointing in correct location. This brings up 2 items for me, first, can you verify for me what the autodiscover record should be aliasing to? I'm currently pointed at autodiscover-rd.hmc1.comcast.net which itself seems like it might also be a cname pointing back to exchange.businessclass.comcast.net.
Second, and more importantly, will this certificate be updated, if this server is being used still?