He's running slack 9.1 so rc.inet1.conf shouldn't be set up to handle wireless yet. The file you want is /etc/rc.d/rc.wireless.conf. You could also manually set it via iwconfig as suggested.
I've always found the default rc.wireless.conf to be on the bloated side and a little confusing. Here is what I ussually do.
Code:
mv /etc/rc.d/rc.wireless.conf /etc/rc.d/rc.wireless.conf.orig
# Then make this your new rc.wireless.conf
# Wireless LAN adapter configuration
VERBOSE=1
case "$HWADDR" in
*)
# Home:
ESSID="MadPenguin"
KEY="b576bdcba1773df06422ac55cb"
# Gypsy Cafe:
#ESSID="2WIRE230"
# Gwens Airport:
#ESSID="Any"
#KEY="421a0f733138f3c93ba20b6089"
# Beth:
#ESSID="synapse"
#KEY="9dd0414685b6ea173a001b7063"
MODE="Managed"
;;
esac
Leave the MODE uncommented always and then just comment/uncomment the particulars of each network where ever you might happen to be. Restart your network after commenting/uncommenting and that should connect you.