Uninstalled and re-installed the version 199 several times. Even the version 123 is presenting the same problem.
Now I uninstalled and restarted my notebook, deleted the C2 folder with the remaining files. I'll try to install it again.
EDIT: Ok,guys, problem solved! It were a matter of complete stupidity from my part. I normally work with my notebook plugged with a monitor, extending the desktop. But now i'm just using the notebook screen, and in spite of using the single screen option, the new object pop-up was opening off-screen.
Thank you all for the help! And sorry if I caused any trouble.