I've run across an issue that does not seem to match the documents and examples located here on the site and in the forums.

I've setup a new datatype of Checkboxlist (using nvarchar). This datatype has about 24 prevalues. When creating the content item, I select one or more of the items in this checkboxlist.  If I check one and only one item, save and publish, umbraco config populates correctly with : 

<subjectCategories><![CDATA[History]]></subjectCategories>

and the database table cmsPropertyData, dataNvarchar column for that contentNode shows  - 25

If I check more than one item umbraco.config saves empty with:

<subjectCategories><![CDATA[]]></subjectCategories>

However, the database table cmsPropertyData, dataNvarchar for that contentNode shows there are more than one - 25,29,30,31,34,70

Shouldn't the umbraco.config show all my prevalues selected comma delimited? Do I have to access this some other way?