What Hardware version is your router?
What Firmware version is currently loaded?
What ISP service do you have? DSL or Cable?
What ISP modem dod you have? Make and model number.
http://forums.dlink.com/index.php?topic=54494.0Somethings to try:
Ensure DNS IP addresses are being filled in under Setup/Internet/Manual? You can copy and paste these from under Status/Device Info/Wan section.
Turn off ALL QoS (DIR only) GameFuel (DGL only and if ON.) options.
Turn off Advanced DNS Services if you have this option under 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? Preferred is WPA-Personal. WPA2/Auto TPIK and AES.
What wireless devices do you have connected?
Any cordless house phones?
Any other WiFi routers in the area?
Turn off Short GI and Extra Wireless Protection under Advanced/Adv. Wireless.
Turn off all anti virus and firewall programs on PC while testing.
I'm just chiming in to let you all know that I have this problem too. I had to log into the router to reset the modem to fix it. It happens about once every one or two weeks