I got the same problem. Well, when security is off, it connects, but with a WPA key is does not work. Well i am not that much further. i can try a different channel, maybe the n900 can only receive on channels 6 through 9 or something, which would suck. WEP encryption in a flat full of students, rather not. normal WPA instead of WPA-PSK ?

Ill post here later on to tell what worked for me.