When I installed my Ubuntu 12.04, I was never asked to enter the root password, therefore I assumed it was the same with my user password. Now, when I want to connect to a wireless, my root password is required. At entering my user password I'm told it's the wrong one. How do I reset my root password?
The root user does not have a password by default in Ubuntu. Instead, your normal user gains root privileges through
sudo or PolicyKit, entering the normal user's password.
You may have forgotten your user's password, or your user may not have sufficient rights to gain root privileges. If both are true, see this question: How do I reset a lost administrative password?
You shouldn't need root privileges to connect to a wireless network, though. Make sure "Available to all users" is unticked in the settings of the wireless connection.
Like Ari Malinen said, your user also has a keyring with a different password. By default, it is set to the same password as the user, but if you change the user's password, the keyring's password won't change with it. Run
seahorse to view your keyring.
Another issue might be that you are actually being asked for the wireless network's password, which is completely independent from your user's password or your keyring password.