Well, do you use networkmanager also with the other computers?
I have also wireless on my laptop, but don't use networkmanager. I use only wpa_supplicant. I would recommend that you connect with wpa_supplicant only and check if it then works.
You would have to make /etc/rc.d/rc.networkmanager not-executable (chmod 644) and then edit your /etc/wpa_supplicant.conf
In your /etc/rc.d/rc.inet1.conf you'll have to configure for wlan (probably wlan0) and wpa_supplicant, there is an explanation anywhere in the internet on the site of AlienBob.
Good luck, I'll have to go to bed now, it's 1 o'clock in the morning here