I was having problems with my upgrade to Windows 8 where my Metro Apps were not connecting to the internet. It turns out, for me, it was a very simple fix and I should have caught it sooner.
I was running last year’s AVG (2012). It turns out they have a new version (2013) that works just fine with the Metro apps, simply replace your old Antivirus/Firewall and you should be good to go.
Also some people from what I read on the forums were having problems because their screen resolution was to low and needed to go to a higher resolution.
Hope this helps!