Create new document library on SharePoint 2010, the Document Template drop down box is empty.

This seems to be a taboo question for Microsoft, since this is a very common scenario and no one seems to be able to answer this question.

We upgraded from MOSS 2007 to SharePoint 2010 earlier this year, we used the database attachment upgrade method. After the upgrade, all the sites under a specific web application have the following issue:

Go site actions > More Options, at the Create Pop up window Filter by "Library".  Select Document Library then click on "More Options" Button.

Under Document Template: The Document Template drop box is empty!

This only happens on this web application. The other web applications that went through the same upgrade process look fine.

How can we add the missing (default) Document Templates back to this drop down?

Obviously, at this point go through the upgrade process again is out of the question. We need to fix this from the current state forward, even if it means to manually add these document templates again.

SharePoint version: 14.0.6137.5000

Thanks!