You have to either backup the origional sprites.png and move it to a directory outside the /graal2001/ directory, and rename your currently one to sprites.png, placing it inside the /graal2001/ directory, or you have to rescript the entire Gui. For a scripter, choose the latter. For a person who can't script, the first is easier.
Oh, if that doesn't work, make sure there isn't a sprites.png inside the /graal2001/levels/ directory.
