I actually had to solve this mystery yesterday. At first, I tried a quick fix : Ctrl + Alt + Delete. then go to task manager, see if explorer.exe is there delete him if he is then go to file->new task and write : explorer.exe. This was a quick fix....
But I wanted to solve this so I wouldn't have to always do this. This appear to be a registry problem so you want to either hit Wkey+r and write regedit then navigate the folders like this :
Once you're on winlogon just click winlogon you should see Shell in the list on the right part of the window. Shell value is explorer.exe if it isn't...there's something wrong... Anyway I deleted Shell. Then went to Edit->New->String key you enter the same value "Shell" then click on the newly created Shell item, right click it. Modify and enter explorer.exe to the value.
This seems to have done it for me. I've also noted that when I created a new user I didn't get any black screen when login on the newly created user.
I know this question is old but oh well Hope this can help someone sometime!