The reason sales of new houses were so low in May is that an expiring tax credit caused a big spike in April. The fact that this article doesn't even mention that when describing the data makes it very suspect.
Well, he didn't say it in the first slide, but if you read on:
"The giant tax credit that the U.S. government was offering to home buyers artificially inflated the U.S. housing market up until April of this year."
Also, it's worth mentioning that you can see the huge dip in the graph when the credit expired, and then you can also see the months after follow the same decline trend as the months before the credit.
The credit propped up that graph, and now it's gloomy again.