For a long time the New Orleans market has lacked a significant residential construction infrastructure, especially in the area of volume construction. With the challenges of Post-Katrina New Orleans no one is ready to rebuild the many thousands of modest residences that sheltered the core of the productive population of New Orleans.
New Orleans may be unique in the extent of damage and the lack of associated infrastructure to repair it. The closest analogy, South Florida has a significantly higher total population, and a lower loss/population ratio. The result is that there was already a large, high volume construction infrastructure , undamaged by the storm. They were able to mobilize and effect repairs largely by redirecting existing resources.
In New Orleans there is no infrastructure for large scale residential construction. All residential construction has been on a small scale for at least twenty years. There is no infrastructure in place which can be redirected towards repair. The scope simply overwhelms the existing local resources.
Many individuals are racing to serve the high income, well insured residents of the "sliver by the river", many companies are rushing to serve the government guaranteed needs of the disadvantaged. No one, as far as I can tell, is moving to address the needs of the vast middle.