That is very unusual. USB wi-fi dongles aren't usually very sensitive, quite the opposite. I can't even get my laptop to connect to the office wi-fi with its dongle unless I move very close to an AP. The N800, on the other hand, is _very_ sensitive. I can see all, or at least most of, the neighbourhood wi-fi networks inside a 200m radius from home. I can even connect to some of the weakest, open ones if I want. I saw the airport hotspot from more than a kilometer away. In town I can sit in the park and connect to a number of coffee shop hotspots from around the park (it's a small park, admittedly). If your N800 doesn't see the network you could check if there's any draft-N wi-fi networks nearby - some of those have been reported to make the N800 blind.