Ug, you've got version A1? If you can, return it and get a B2 model. Looks like they've stopped releasing updates for the A1 version. The B2 version is up to firmware 2.24. Any of the 1.xx firmware seems to be really flaky, similar to what you are seeing.
My B2 came with firmware 2.20 and it pretty much didn't work, got the constant dropped connections if I was able to connect at all. Once I upgraded to firmware 2.24 I haven't had any problems (See the occasional cryptic "received deauth" in the log, but everything seems to be working fine and stays connected with no dropouts that I've experienced.)
If you log into the router, click on the Status tab, and scroll down to the Wireless LAN section, what are you seeing next to "Wireless Radio"? Until I updated my firmware, I usually saw "Wireless Init Failed". Now that I'm running 2.24, I get "Wireless Radio: Enabled" which is much better! However, with the A1 firmware, the last update is the 1.10 version, so I think you might be stuck.
Looks like some DLink exec forced a product out the door before it was ready. Probably every techie in the place was screaming "Noooooo", but just like the place I work, the execs tend to value a schedule date more than a working product. Probably explains while the tech support line is so swamped. But, then again, I'm allowing work frustrations to affect my answer here.
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