its most likely an issue with your modem or ISP.
I've had this happen a few times in the past. Have you tried going to another location with your Macbook like Starbucks or McDonalds?
You'll need to call your ISP and tell them you're having issues accessing websites. They will take you through 87 different steps, but just say you are doing them. They can reset things on their end, but at my old office, we had this all the time with Comcast for some reason.
Try this:
http://www.tomshardware.com/forum/50...orks-elsewhere
or the easiest answer is often the correct one... they banned you
