The folder only being 20mb would explain why it's black. The game should download about 300mb of content when you start it up. If the popup doesn't come up to allow administrative privileges (on Windows Vista or Windows 7) then that's the problem. Also clicking No on that window will cause the issue and not allow the program to write files to disk in the proper location.

If you right click the shortcut is there an option to Run as Administrator? If so do that and it should download all the files, and your folder should be around 380mb.