Here's how you fix it:
Go to the DNS portion of your Network settings. Write down your current settings (just incase you want to go back to them). Then change your DNS to:
8.8.8.8
8.8.4.4
This is the Google Public DNS settings. I was having issues all day, then I changed my settings and BAM! Downloaded right away. Now, I did change back to my original DNS settings because I don't know how secure Google is, but if you pop over to their DNS, you should be able to get the update.