You should really give more useful information such as OS, model of Netcard, g or N mode etc. Without any real information to troubleshoot, here are my suggestions based on experience.
I doubt that the router is at fault. My router has always been rock solid on wireless.
On your wireless workstation, don't load or use the dlink utility, it sucks. Use the Microsoft "Zero" to configure your workstation.
Download software called "Netsurveyor" from the NET. This will identify any conflicting signals so you can manually select a channel that is totally free. Do not use the router to automatically choose the channel if the workstation is far from the router.
If the NETcard is USB, make sure you have the latest drivers.