other SSH servers on the same network or on the internet? if you have never connected to an SSH server on the wlan, maybe your router (or the windows xp firewall) is really blocking that? are your lan and the wlan in the same subnet? the next step would be to use some network monitoring software on the laptop and/or your router. maybe that'll give some hints... try to compare what happens when you use ultravnc and when you use ssh. other than that, i'm at a loss, sorry...