No wireless

I have been using Ubuntu for a year and a half. Since Hardy Heron. When I installed it my wireless worked immediately and never had a flaw. I have always updated when the alerts came along. The last update was one that completely changed my desktop and the way things work. I am getting used to a lot of it but my wireless stopped working. A box opens up and asks for authentication. I fill in the password and after a second or two a box appears that says connection established. After about 5 seconds the connection is lost and the authentication box opens again. I have been trying to login for days. I have restarted several times with no change. The new operating system is Ubuntu 12.0 4 LTS. My computer knowlege is very limited. Chances are if you ask a question it will be necessary to instruct me how to find it on the computer.

Some thoughts.

One thought is is to use or run the desktop using the CD of an old version of Ubuntu (you shouldn't need to actually install the operating system, you just need to see if you can access the internet or not), e.g. an old CD of Hardy Heron, to see if the problem also happens with that version of operating system. I know it sounds stupid, but if you don't feel confident doing this or aren't familiar with that version of operating system, then do a backup of your important files first. I would rather be considered stupid because I told to you waste your time doing a backup than to be considered stupid because I didn't tell you. If you still can't connect to the modem, then that would suggest the problem isn't the Ubuntu 12.04 itself.
One thing you will need is the modem manufacturer's handbook. If you don't have one, then search for a PDF on the internet with a search engine.
Lastly, do you own the modem or is it rented?

Thank you so much

Thanks for taking the time to discuss this, I feel strongly about it and love learning more on this topic. If possible, as you gain expertise, would you mind updating your blog with more information? It is extremely helpful for me...thanks.