if you're running wireless and trying to connect to an unencrypted network, try this in your /etc/rc.conf

ifconfig_ath0="up"

you would replace ath0 with your detected wifi device (try dmesg |less for this) - you can try rebooting, or /etc/rc.d/netif restart to get it to latch on once you do this. for a WEP network, try (/etc/rc.conf again)

ifconfig_ath0="ssid SSID wepmode mixed weptxkey 1 wepkey KEY DHCP"

where SSID is, that's right, your ssid and KEY is your WEP key. use 0x at the beginning of the key for hex or nothing preceding for ascii.

to retry your device connection, try this simple script:

#!/bin/sh
rm /var/db/dhcli*lease*ath0
ifconfig ath0 down
ifconfig ath0 up
dhclient ath0


if these answers don't help, it's time to read the freebsd handbook. check out /usr/share/doc/en/books/handbook and look for the network-wireless chapter.

best of luck.