This may be a lengthy description, but I just wanted to be as forthcoming as I could, as I was annoyed by the lack of support I was able to find to fix this problem myself. As far as I understand it, the problem is in the router. I don't know what it "thinks" it's doing, but the solution detailed below will essentially just tell it to do the basic things it should be doing.
What I had to do to fix this (Same router model, same issue) was to unplug every cable from the back of the router (including the cat-5 cable coming from the modem and going into the WAN port), except for the computer that I know works when plugged directly into the modem. I left the modem turned on, though disconnected from the router.
The point of this was to have a simple connection between computer and router so that I could get into the router and tweak its settings. For some reason it was freezing up on me when the modem was plugged in and I could not access the router at all. So, after plugging in only this computer to the router, I unplugged the power to the router, waited about a minute, and plugged it back in. When the router first turns on all of the lights on the front come on. Wait for all of the numbered ones to go off (by 'numbered' I mean the lights numbered 1-4 on the right side of the front panel display) except the one that corresponds to your computer's connection port in the rear of the router (the number your computer is plugged into).
Once this has happened you should be able to get into your router through a web browser by putting "192.168.0.1" (no quotes) into the address bar. The default username/password combination (which you should be prompted to put in) is "admin" for the user name, and leave the password field blank.
You should now be viewing the router's page, which should by default be showing the "SETUP" tab. If we cant fix the router by renewing your DHCP (as detailed below), then we will return to this page.
For now, plug the cable from the back of your modem into WAN port on the back of the router. Click on the "STATUS" tab (3 buttons to the right of SETUP), and look under the "WAN" heading. Note that the settings (I'll refer to them as "WAN Settings") displayed under this heading are as follows:
If it says "Connection : DHCP Client Connected" and there are numbers besides just zeroes for the lower WAN settings, then your internet should be working. Verify this in a new window by attempting to browse to your homepage or google or something. If it does not work, or if the Connection status is not connected, then click the "DHCP Renew" button directly to the right of the "Connection" setting.
A number of things could happen here. If it works, the WAN settings should no longer display only zeroes (you may have to navigate back to this page). If the DHCP renew attempt times out or doesnt work, then navigate back to the "SETUP" tab on the main page of the router (the page we started on).
There should be a button in the middle of the page under the "Internet Connection Wizard" heading labeled "Setup Wizard". Click it, then click it again as it changes to "Launch Internet Connection Setup Wizard". The four steps are:
- Step 1: Set your Password
- Step 2: Select your Time Zone
- Step 3: Configure your Internet Connection
- Step 4: Save Settings and Connect
For the "configure your internet connection" step, click the button that copies your MAC address. At the end of this process your router will be reset. Again, wait for the lights on the front of the router to display properly before signing back in. You will have to sign back in afterwards using your new password (admin should still be the username). At this point it worked for me. If it is still not working, go to the STATUS page again and renew the DHCP (same step as before) now that you have run the setup wizard. Good luck, hope this solves it for ya!