Update This wiki page on the Ubuntu site addresses this issue in full.
Following the resolution problem with Ubuntu 8.0.4, the next hurdle I had was getting my slim apple keyboard to play nice. Due to driver updates, after logging into Ubuntu the keyboard becomes unusable. I later read this post which reassured me that I wasn't going mad. (or madder than I currently am!)
"pressing "Clear" (numlock key) results in right part of the main keyboard part (keys g-l on the middle row + keys around) to behave as a numeric pad. To set it back, I found after lengthy trial-error, that I have to press F5 (or F6, I'm not sure)."
After banging the F6 key, my keyboard returned to normal. Phew. The only problem now was that the function keys performed as if the previously vestigial Fn was pressed the whole time. So for example if I pressed F1, it would decrease the brightness of my laptop screen! How annoying!
After digging around the I found a this excellent post which helped me turn off the default Fn key behaviour for apple keyboards.
To get your apple keyboard back to how it functioned in Ubuntu 7.10 do the following:
1. Add a file to the /etc/modprobe.d/ directory with the following contents:
options hid pb_fnmode=2
This turns off the default Fn key behaviour of always being on.
2. Add the following to Preferences->Session->Startup Programs section:
xmodmap -e 'keycode 77='
This turns off the mapping for the "Clear" key (keycode 77) on the apple keyboard which is wreaking havoc.
3. Restart your machine and enjoy the normality :)
This is now a bug. Hopefully it will be resolved soon.