Devices stay connected to network, but no longer have access to it

I have a WNDR3700v1 router. Among other devices, I have a laptop wirelessly connected to it and a network printer hard wired to it. Ever since I purchased the router, I have had an issue where they both randomly lose connection to the network. If I check the laptop it still shows that it is connected to the router. If I check the printer it shows that its connected to the network.

For the printer, I need to turn it off and back on again to be able to print to it. For the laptop, I disable the wireless and turn it back on and it reconnects fine. Within 3-4 hours it happens again.

This is not an issue with the printer or laptop, as I tested my old WRT54G for a few days and it worked fine without any issues. The minute I added my WNDR3700 back it started happening again.

I have also tested the same router that my brother has with DD-WRT on it and it does not have the same problem, though other problems do popup.

So I am wondering if I have a setting wrong on the router or if this is a known issue?

Anyone have any suggestions?

Thanks