Unity 4.5x doesn't start on Windows 7

Hello, this is my first post so do not know if this is the right place, i have a problem, I downloaded the Unity 4.5.0 Free, and when I click the Unity icon, it goes to the splashscreen, as it should be, then it goes to the screen that follows the splashscreen, and when I actually start it, it will not start, I click the button to start and then nothing else happens, I clicked on the icon again and appeared that was loading the assets, there appeared a message that I can not remember right (horrible memory), what is that ???

Sorry my poor english, i’m brazilian

If you open the Unity log, do you see anything interesting? If in doubt, attach it here. Its path is /AppData/Local/Unity/Editor/Editor.log.