in the routers device status page, is it showing that it's using 40mhz mode? as well as a primary and secondary channel?
btw, dlink i noticed that it seems to use an overlapping channel for the secondary and is always four channels from the primary, Do you think it's possible to have the router detect the "best" channel for both the primary and the secondary separatly?.. Now back to our topic.
Can you give two screen shots of the drivers properties page? first screenshot showing the first list of options and the second screen shot showing the rest of the options available when you scroll down the list?
It seems that the driver is stuck using G mode for some reason if the max you getting is 54Mb. Even if you have locked the gateway to N only mode. Difficult without any other N devices to see if it's the routers problem or the laptops problem. I can attest though, that my laptop wireless G is bunkard because it never connects at 54Mbs I get 48 Max but usually less.
anywas gimme a screeny of those driver settings, or if it's a usb or pci-e laptop card, send it to me and i'll see if I can connect with it.