Version details: 1.4.5
Distribution/Version: XP SP2

A nested class that is under the private section of another class shows up in 
the documentation that doxygen creates for that class. If you create 
documentation for this private, nested class, doxygen displays the first line 
of it for the the private, nested class.

Here is an example:

class ToFu
{
public:

private:
    /**
      * The first line of this documentation shows up
      * under NestedToFu class documentation.
    class NestedToFu
    {
    public:

    }// end NestedToFu class

}// end ToFu class