This script assumes you’ve initialized ‘startText’ in the Inspector through drag and drop. If this scrip is attached to the GUITexture object, you can add the following to the top of the Start() function to fix the problem:
if (startTexture == null)
startTexture = guitexture;
This initializes ‘startTexture’ to the guiTexture attached to the current game object.
Or you can just drag and drop the game object that has the GUITexture onto the ‘startText’ variable.