The router could be using a MAC filter. MAC = Media Access Control #, not MACintosh. It's actually what I use on my own home network since there's a few devices I have which don't support WPA (and WEP's useless) and there's quite a bit of transient traffic with friends' laptops, phones, and other wireless devices wandering through. To do it the other ways, I'd have to give all of them the password to my router, not ideal. You would get a similar type reaction from my router. You'd "connect" but all packets/traffic would be blocked.

If you see a "linksys", that just means someone bought a Linksys router and did minimal configuring (if any) to it. If they're too lazy to set up their own router, all bets are off to its reliability.