I had about the same problems as well, and came to find out that the firewall in the router and the firewall in the cable modem were conflicting one another.
You need to call the router customer service or they may have a chat box on a website of their company that you can chat with a tech support rep there.
Tell them what the problem is and they can guide through the process of disabling the firewall in your router.
*Remember you only need the firewall in your cable modem to be safe*
Hope this helps!
