There are no such things as "stupid" questions. However if you think your question is a bit stupid, then this is the right place for you to post it. Please stick to easy to-the-point questions that you feel people can answer fast. For long and complicated questions prefer the other forums within the support section. Before you post please read this
Have you updated everything with MintUpdate? Also, why are you using Mint 12? I believe that support for Mint 12 will stop next April. Mint 13 is a LTS, so it will be supported for a few years. If you want the latest version, Mint 14 is out now as well. If your system works fine with mint 13, definitely install it instead of Mint 12. If everything is up to date, and you still can't install it, use Synaptic to install packages.