This morning I finally decided to install the latest Mac OS X 10.7.3 update. Everything went better than expected! The only exception was when I connected my external display. The image kept flashing and I couldn't see anything. After some testing, I think I've found the solution:
- Open System Preferences.
- Click on Displays.
- Show display in menu bar.
- Click on the menu bar icon.
- Check if the selected screen resolution for the external display is appearing twice on the list.
- If it's there twice, select the other one. If it's not, I'm really sorry! :P
- You can remove the icon from the menu bar now if you want.