I am having a very similar problem. My wireless drops out constantly. The D-link gadget stops showing speed status and instead says IP Config error. I have enabled MAC filtering and assigned reserved IP's for all of the MAC registered devices. When I start a download of any sort of even access websites like Amazon, the wireless drops. This is driving me nuts and I am seriously regretting the purchase of this router. I am by no means a networking wizard, but I never had any difficulties with my Netgear.
I have a desktop running Vista connected to the switch. I have no problems with the connection there. I also have an XP laptop, a Vista laptop, an Ubuntu netbook and a Playstation 3. They all have the same problem. Any ideas?