Just a thought: (A few actually)
-Did you set up a MAC restricted access list on your router at some point in the past? If so, obviously you'll need to add the Debian PC's wireless MAC address to the 'allowed' list.
-Is your router on channel 12 or 13 by any chance? Historically, the official wi-fi Spectrum in the USA only seems to have included channels 01-11, whereas we here have the additional 12 and 13.
Since the USA is the largest technology market in the world a significant amount of wi-fi enabled stuff is configured by default for that market, not ours, and may not work on wifi channels 12 and 13. When you install a wi-fi card under Windows the manufacturer supplied installer usually asks you for the region the card is being used in and resets the channel range accordingly. Unfortunately, they don't tend to supply such friendly installers for Linux.
I have personally encountered a good example of this syndrome: The original grey single-antenna wireless 'g' adaptor for my Xbox 360 can not see any network on channels 12 or 13 - it is an American designed product designed originally for the USA market, and the version sold to the wider world appears to be exactly the same 11-channel unit. It, or my example at least, can not see any network on channel 12 or 13.
Finally, a re-iteration of some useful advice I originally received in this forum - if the router at the heart of this problem is set to mixed WPA / WPA2 encryption mode, go into the router's settings and try setting it to WPA2 only - that solved a WPA2 connection problem for me on at least one subsequent occasion.