ESRI.ArcGIS.DefenseSolutions.CoordinateToolClass

Hi,
I am really confused.
I setup Military Analyst 10.0 to use DefenseSolutions.
I wrote a VB.NET Application (2010) which uses DefenseSolutions.CoordinateTool for coordinate conversion.
It is OK.No problem.
Now I am creating a Web Service on this machine which performs above process.
But when I use this service in a VB.NET 2010 Windows Application, when I call the method for coordinateconversion
it gives this error : "Unable to cast COM object of type 'ESRI.ArcGIS.DefenseSolutions.CoordinateToolClass' to interface type 'ESRI.ArcGIS.DefenseSolutions.ICoordinateTool'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{....... }' failed due to the following error:No such interface supported (Exception from HRESULT:0x80004002 (E_NOINTERFACE))"

In the service the code is as below:

public function ......

dim pCoordTool as ESRI.ArcGIS.DefenseSolutions.ICoordinateTool
pCoordTool = new ESRI.ArcGIS.DefenseSolutions.CoordinateTool (I tried CoordinateToolClass, but the same error )

pCoordTool.ConvertLocation(vValue,iFormat,vFromDatum,vToDatum,pPoint1,pPoint2,DMS,UTM,MGRS)

.
.
.

end function

I see from the application that when I call this service method, the ConvertLocation line gives error..
I tried to use pCoordTool.GetDatumList method but it also gives error.

I think there is something wrong with the declaration.
In the creation of service, Iam binding and initializing the Engine Product.

Really important...
Any ideas?