What HW version is your router?
What FW version is currently loaded?
What ISP Service do you have? Cable or DSL?
What ISP Modem do you have? Stand Alone or built in router?
What ISP Modem make and model do you have?
Ensure DNS IP addresses are being filled in under Setup/Internet/Manual?
Turn off QoS options.
Turn off Advanced DNS Services if you have this option Setup/Internet/Manual.
Turn on DNS Relay under Setup/Networking.
Setup DHCP reserved IP addresses for all devices on the router.
Ensure devices are set to auto obtain an IP address.
Set Firewall settings to Endpoint Independent for TCP and UDP.
What wireless modes are you using?
Try single mode G or mixed G and N?
What security mode are you using? WEP, WPA or WPA2? Preferred is WPA2 and Cipher type to AES only if your device support this.
I am having the exact same problem with my DIR-655. Internet would intermittenly disconnect and then come back online again. MSN and ping in CMD would work continuously. Funny thing this applies randomly, sometimes all the computers can't go on the internet (wifi or w/o wifi), sometimes only one of them won't work. Rebooting the router through control panel sometimes fixes the problem. Interestingly I am also using Time Warner but I am in SoCal area.