A Second Look at the Ontological Argument

In response to the last post on the Ontological argument, the following video was recommended: http://www.youtube.com/watch?v=sHXq_8n2O1I&feature=related (I thank the person who posted this!)

Before going further, I would like to encourage everyone to read the first post on the Ontological argument! (http://www.youtube.com/watch?v=sHXq_8n2O1I&feature=related) Due to the abstract nature of the argument, it would basically be impossible to understand this post or the video mentioned above without gaining some experience on the topic.
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First of all, I do not think that any of my reasoning in the first post has been overturned by the second video from Dr. Craig. It is helpful to watch the second video, however, because it becomes easier to see Craig's error.

Consider what Craig said concerning point #3:
"If a maximally great being exists in one [possible world], then he exists in all of them."

A better rewording of the above statement would be:
"If a maximally great being exists in possible world X, then he exists in all of them, according to possible world X"

But if possible world X is not a valid possible world, it doesn't matter what it contains. Those contents cannot jump into other possible worlds. Even if some entity had the ability to jump from one possible world into another according to possible world X, if possible world X is not valid, then the entity cannot jump into other worlds.

Conclusion:
As with the previous discussion of Craig's presentation, the assumption that all possible worlds are valid has still not been justified. While I may have red hair in one possible world, the reason I do not is because that possible world in which I do have red hair is not a valid one (don't get any ideas). We are still left with the task of determining which possible worlds are valid, because the existence of anything in any possible world is dependent upon the validity of the possible world itself.