The "File"."New Knowledge Document" and "File.New Knowledge Tree Document" menus are disabled as long as the user has not set the focus/preselected a specific knowledge category. The reason for the disabled menus is not really obvious to the end user.
Enabling this and ask for a category selection up front - e.g. by a simple popup message (which may just provide that hint to the end user and get them back to the previous window) or a category selection list to follow up with the creation of the knowledge document would provide a simple step forward in regards to ease of use.