Before I tossed my DIR-655 into the recycle bin, I decided to look inside once again, and after I opened the case I noticed something I hadn't noticed before: the circuit board holding the Atheros processor was slightly out of place, enough, I thought to compromise the connection at one side of the board. I wiggled it out, and then re-seated it ...and when I powered up the unit again the wireless LED was flashing!
I have put the 655 back into my system, and everything is back to normal. Yahoo!
I think it's incredible that it took an almost-8-ft drop onto a concrete floor, and other than jarring a circuit board out of its socket a bit, no damage was done. Thanks for making such a rugged product, D-Link!!