It's a LONG TIME known problem with Some routers including specifically AT&T Uverse, which there building out here and dropped by toget some pre-orders in last week - But I digress.
So, I'd do some simple things first, which could resolve it before getting deeper. Try turning off your firewall on the laptop, then connect, then turn it back on... I've experienced this for 6 weeks and tried all contortions while visiting family and it turns out there was a problem between router wall and MacBook which didn't play well together on the playground.
I'd search for solutions. Some of them have been simply as to use a Google DNS - SO I'd TRY THAT now, 
Get Started | Public DNS | Google Developers
You might try holding option button plus the wifi signal symbol at top of desktop:
then click on open wireless diagnostic & run;
It can also be as simple and going to a manual designated DHCP address:
Or there's another try of a network change that can work;

You can try also to rename two broadcast radio network names differently and connect only one a time.
Others involve resetting some config settings either through the browser and or on system preferences... save this for later.