Assume that a document library is configured to have multiple content types in Microsoft SharePoint Server 2010. When you save a new file to the document library for the first time, you are prompted to select a content type for the file.
To resolve this issue, apply the following hotfix updates:
2536591 Description of the SharePoint Foundation 2010 hotfix package (sts-x-none.msp): June 30, 2011
2544019 Description of the SharePoint Server 2010 hotfix package(dlc-x-none.msp): June 28, 2011
After you apply these hotfix packages, set SPList.ForceDefaultContentType to True for the document library. To do this, use the following PowerShell command:
Note The hotfix packages add a new ForceDefaultContentType property to the SPList object. The default value for the property is false, and the property can be only changed programmatically.
If the ForceDefaultContentType property is set to false. You are prompted to select a content type for the file when you save the file that is created through Office 2010 client to a SharePoint document library. From a programmatic perspective, the Lists.GetListContentTypes web service returns a collection of all the content types in the SPList.ContentTypescollection.
If the ForceDefaultContentType property is set to true, the file that is added as a new item is assigned the default content type for a list. Therefore, you are no longer prompted to select a content type. From a programmatic perspective, the Lists.GetListContentTypes web service returns only the first content type which is the default content type for the list in the SPList.ContentTypescollection.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.