Sorry that didn't work. To enable the package containing the bcm43xx-fwcutter package, go to System>Administration>Software Sources. Under the 'Ubuntu Software' tab, you will have a list of software sources under the heading 'Downloadable from the Internet'. Make sure that all the boxes in this list are checked (and in particular the box for the 'universe' repository, which I believe contains the package you need). Then close the window. If you're asked about reloading the sources list, say yes. Then try running these commands again:
Hopefully it will work this time.
sudo apt-get update
sudo apt-get install bcm43xx-fwcutter
HOWEVER, I was thinking about this today and seem to remember that the bcm43xx driver in Ubuntu 7.10 did not support some wireless cards in certain Macs--even though it claimed the card, the card wouldn't work with it. This has been fixed in later versions of Ubuntu, but I'm afraid that even with the bcm43xx-fwcutter package installed, your wireless card may not work. If you still can't get your card working with the instructions above, please post the output of these commands so I can look up your exact wireless card model to see what the status of it is in Ubuntu 7.10:
And also please let me know whether your Mac is Intel or powerpc-based.
lshw -C Network
If bcm43xx won't work, there are other ways to get the card running, so don't give up. Sorry this is becoming so complicated; unfortunately, I'm a bit out of practice when it comes to Gutsy.