Why is that some controls are shown only in the insertable column and not in control column.

i made an activeX control in VC++ and registered it. It is not coming in control column of the Component dialog box in Visual basic 6.
In ActiveX control class there is a function afxOleRegister().In that i set the parameter to afxApartmentThreading. Still the control is not showing up in the control column of the Component dialog of VB 6.

Is there some problem with the interfaces i designed.Plz help me out.