SharePoint Site column default value not pre-selected

After fiddling with SharePoint custom content types for a while, the default values on my choice site columns in my document library suddenly refuses to work. Although a default value is being set, the items are created with these field being blank, where it suppose to fill in with the defined choice default value, as stipulated in the content type’s site column.

Apparently, the content type has to be set as the document library’s default content type, else the choice column’s default values will not be pre-selected. In addition, if you have multiple content type that uses the same choice site column, setting any one of content type as default content type would make the other content type works too.

Ref: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1706972&SiteID=1