The size of the world window is determined by the 'super' call in your world constructor. This one should be something like this: super(120, 400, 1);

You have to make it the right size, danpost doesn't necessarily know the size needed. You're using a little bit of the world, so make the world the same size as the amount of space your using now.

Try updating it again -- this time lock the scenario (check the 'Lock scenario' checkbox). Maybe that will fix the size of the world (possibly a bug when scenario is not locked).

My guess, now, is that it is a problem with the version of greenfoot you are using. You may want to shoot an email to support@greenfoot.org.