I'm doing my Cert IV and they have discouraged me from using Linux so I'm amazed that your introduction to it was while you were doing the same course. Anyway that doesn't help with your problem.
Unfortunately your description of what has occurred isn't all that clear so what I am about to suggest is purely based on my experience for getting Ubuntu to connect to the net. If that works for you great, if it doesn't we are going to have to work through it methodically.
OK, I want you to read this post
and follow the procedure outlined in it. Basically what it will do is reset your DNS. I know from experience that Ubuntu doesn't automatically connect in Australia, hasn't since 7.10 (Gutsy Gibbon), and this little hack helps.
Let us know how you go.