Hey jwc, I'm no Linux expert - I just played hit or miss until something worked. Someone who knows more may be able to to give you better guidance.
So with that fair warning, here are the steps that got things working for me:
1. If your machine has a hotkey on/off switch for wireless, I'd recommend disabling it to avoid conflicts. To do this. restart your machine, enter BIOS setup, and disable WIFI hotkey (by default, Fn + F2 turned my wireless on or off)
2. Remove ipw3945 components via Yum ($ yum remove ipw3945)
3. Configure freshrpms repo for Yum:
$ sudo rpm -vhi
http://ftp.freshrpms.net/pub/freshrp....fc.noarch.rpm
$ sudo rpm --import
http://freshrpms.net/RPM-GPG-KEY-freshrpms
(To avoid update conflicts, you'll want to configure yum to disable the freshrpms repository by default and enable it explicitly in Yum commands when you want to access it.)
4. Install freshrpms ipw3945 components via yum:
$ yum --enablerepo=freshrpms install ipw3945
(Yum displays a list of packages and dependencies - make sure that dkms-ipw3945 is included. If it isn't, install it separately afterwards.
5. Restart machine to incorporate new components.
These next steps were key for me.
6. If it's on, turn off 'network' service ($ service network stop)
7. Check status of NetworkManager and NetworkManagerDispatcher - if not running, turn them on (you may want to have these automatically turned on at startup and have 'network' automatically turned off - NetworkManager can manage both wired and unwired network connections).
8. Activate card and kernel module ($ /sbin/ipw3945d --quiet).
If it worked, you should now be able to browse available networks. I just click my nm-tool icon in the icon tray to see a list. Hope it works for you.
Assuming it works, you can turn off the card thusly:
$ rmmod ipw3945
$ /sbin/ipw3945d --kill
Good luck,
Stuckey