Fighting with the iwl3945 several night, I decide to reinstall FC8 again but this time, it does not detect the wireless card at all. At the end, I found the solution:

Add this line to etc/modprobe.conf:

alias wlan0 iwl3945
options iwl3945 disable_hw_scan=0

Then restart, you will send iwl3945 in the Network configuration (System > Administration> Network).

You can now try to activate the wlan0 but for me, error occur as the iwl3945 is not configured correctly.

# more /etc/sysconfig/network-scripts/ifcfg-wlan0
# Intel Corporation PRO/Wireless 3945ABG Network Connection
DEVICE=wlan0
BOOTPROTO=dhcp
HWADDR=00:18:de:b2:de:17 << I added this MAC by hand
ONBOOT=no
DHCP_HOSTNAME=tosca.opera.univ-pau.fr
IPADDR=
DOMAIN=
NETMASK=
TYPE=Wireless
ESSID=
CHANNEL=1
MODE=Master
RATE=Auto
USERCTL=yes
IPV6INIT=no
PEERDNS=yes

Also, I have to install pam_keyring (yum install pam_keyring) and modify the /etc/pam.d/gdm:

# more /etc/pam.d/gdm
#%PAM-1.0
auth [success=done ignore=ignore default=bad] pam_selinux_permit.so
auth required pam_env.so
auth optional pam_keyring.so try_first_pass —- add this line
auth include system-auth
#auth optional pam_gnome_keyring.so —- comment that one
account required pam_nologin.so
account include system-auth
password include system-auth
session required pam_selinux.so close
session include system-auth
session required pam_loginuid.so
session optional pam_console.so
session required pam_selinux.so open
session optional pam_keyinit.so force revoke
session required pam_namespace.so
#session optional pam_gnome_keyring.so auto_start —- comment that one
session optional pam_keyring.so —- add this line

FC8 installed without Network Manager and Network Dispatcher run at startup, so fix it in the Service configuration.

Restart computer, now the error show when activate wlan0 might be the cause of my Dell: dhcp error. After a lot of googling, I figured out that ndiswrapper is not install. Then, I install ndiswrapper 1.5 (from ndiswrapper wiki site) and restart the computer again.

Now, wireless works perfectly.