Tablet Connection Woes

You guys have never let me down, I'm googled out and cannot figure out what is really causing this problem.
My niece has this cheap ass android tablet and suddenly it cannot connect to our network.

-For many months it connected to our secured network just fine, I even tried a complete factory restore on the tablet. It is a netgear 300 router

-I have cancelled and forgot the network, and then went ahead and reentered the network password. It shows clearly that it is connected to the network and there are no authetication issues. BUT ... it will not pull up a web page. getting web page not found error.

-The tablet does show in the wireless devices section of the router settings.

-the ONLY time I have gotten to pull up a web page was by going into the router settings and unchecking this thing called QoS. There was this multimedia setting right at the top... I disabled it, applied the setting than all of a sudden it pulled up a webpage.

-But... shortly after, it didnt connect to a page. Going back and enabling that QoS setting, applying ect. made it work properly... Its so strange because it almost didnt matter what setting you choose will allow it find a webpage... and it is more the physical making of the change is what made it be able to pull up a web page.

-Unfortunately, it is not really fixing the problem, because after a period of time the tablet goes back to the original problem .... shows is connected, but won't pull up a web page.

I would sure welcome any thoughts or suggestions on what else I can do.

This looks like a problem with your router. Did you try to connect on a public network - e.g. McDo - and did it work there.

It would still be interesting to see whether the device works on another router. Just to make sure on which side of the fence to look for the problem.