You might need to refigure your screen. I also have my game size set at like 1350x1200, or whatever it is. Contact Support, they should be able to tell you what's up.
When I am in the login I cant get to the password and username to play wizard101 because screen is to big is there a way to zoom out.
When you bring up the login, left click on the blue band at the top of the screen and push it up a little to see if it will help raise the username and password slots up enough to use them. Unless your task bar is wider than normal this should help.