LISP Program Renders Existing Blockreferences Undefined

I have a C# application that calls a LISP program to insert blocks into a drawing. When I run this LISP program from the C# interface it renders all existing blocks with the same name as: ** Undefined block #2129780480

The process is:

1. I use the INSERT command from the command line to place a block called REVISION in the drawing.

2. I then run the C# application which calls the LISP program that inserts the same block (REVISION).

3. The block reference inserted from the command line becomes undefined.

The code I use to call the LISP program is:

//Get a reference to the active document

Document doc = AcadApp.DocumentManager.MdiActiveDocument;

//Convert the document to an Interop version

AcadDocument curAcadDoc = (AcadDocument)doc.AcadDocument;

//Send the Visual LISP Load Command to the editor

curAcadDoc.SendCommand("(vl-load-com) "/*space after closing paren!!!*/);

//Which size Titleblock is being used (D or F)

if (TitleBlockSize.Equals("D"))

{

//D Size Standard Width Device List

if (this.radioButton1.Checked)

{

//Set up the full path to the LISP program

string lispPath = "Z:/NPID16/HCAD/DLIST20";

//Format the string to load the specified LISP program

string loadStr = String.Format("(vl-load-all \"{0}\") "/*space after closing paren!!!*/, lispPath);

//Send the formatted command to the editor

curAcadDoc.SendCommand(loadStr);

//Now call the LISP program

curAcadDoc.SendCommand("_DLIST20 ");

}

}

If I load and run the LISP program outside the C# application there are no problems.