If you have an un-updated copy of Fedora 7 then you may find that you will have trouble getting the 3945 to work.
That was a fairly general statement because I wasn't sure just how up to date you copy of F7 was.
The situation as I see it is this.
When Fedora 7 came out it used the iwl3945 driver, and looking in the original Fedora 7 repositories here:
the firmware released at that time to go with the card was something called "iwlwifi-firmware-2.14.3-2.noarch.rpm".
A lot of people including me could not get our card to work with that combination and turned instead to the ipw3945 modules and firmware from the ATRPMS repository.
If you didn't specifically enable one of the rarer Fedora third party repositories, blacklist the iwl3945 software and use the ipw in its stead then you were one of the rare people for whom the original iwl3945 worked.
When Fedora 8 came out it had updated iwl3945 software with a specific firmware package, iwl3945-firmware-126.96.36.199-1.noarch.rpm. The actual numbers may not be the same but the principle holds good.
This newer iwl3945-firmware-188.8.131.52-1.noarch.rpm filtered down into the Fedora 7 repositories sometime in September/October.
rpm -q iwl3945-firmware
will confirm that you have it.
NetworkManager has also changed a lot during the currency of Fedora 8 and has presumably filtered down to 7 and one thing concerns me about your setup.
and attempting to activate it brings up those errors I mentioned in the original post
If you are using NetworkManager, you must not try to control the card from the "Administration - Network" dialogue which is identified on its title bar as "Network Configuration". There are two different ways of controlling a wireless card in Fedora and unfortunately they conflict with each other.
If Network Configuration is set to start your card at boot time then NetworkManager won't get a chance. But if NetworkManager is trying to control your card the Network Configuration won't be able to.
Try going into KDE main menu - Administration Menu - Network, highlight your card and click "Edit". Make sure that "Activate Device when Computer Starts" is NOT ticked and that "Controlled by NetworkManager" (if it is there) is ticked. Reboot the machine and try the card again from the KNetworkManager applet in the Notification Area of the Panel.