After you get the blank screen, ( After logging in. )
Press either Ctrl+Shift+Esc, or Ctrl+Alt+Delete.
Once you do that, the task manager should open up.
Once open, go to processes and look for Explorer.exe, You might not find it, Because sometimes apparently Vista forgets to start it.
If it is there, Right click it, and End Process.
Once done, ( Follow this step if it isnt there also. )
Go to the Applications tab, and click 'New Task...'
Type in Explorer.exe
This should force the GUI to load, and you shouldnt have any problems from there...
If your computer is new, I'd suggest getting the new Drivers also, as this may reduce the number of times you'll have to do this.