assertion error with C++ Dll using CDialog

Can anyone help me with this?

I’m getting an assert error when I exit out of my main app (C#) after calling my dll (C++). The error is Debug Assertion Failed! Program:… File: f:\...appcore.cpp Line: 862. I’ve researched this problem and it appears I needed AFX_MANAGE_STATE(AfxGetStaticModuleState()); which is the first line in the dll function but the problem still exists. I also am using debug versions on my main app and dll. This assertion error only occurs when I’m calling a function that generates a dialog box (CDialog). When I call other functions that do some calculations there are no errors. I’m using Visual Studio V2005. Here are the code excerpts. Thanks in advance.

Code:

/// code from assertion appcore.cpp
	// Cleanup DAO if necessary
	if (m_lpfnDaoTerm != NULL)
	{
		// If a DLL, YOU must call AfxDaoTerm prior to ExitInstance
		ASSERT(!afxContextIsDLL);//here is where things stop
		(*m_lpfnDaoTerm)();
	}

/// code from DLL (uses MFC as shared DLL)

extern "C" int EXPORT Get_The_Material(char  *MaterialName);
								  
{
//Microsoft suggests this macro to be called first, see above
AFX_MANAGE_STATE(AfxGetStaticModuleState());
	
if (IDOK == FM.DoModal()) {
	if (FM.iItem != -1) { // user selected a material
……… rest of code
}}
Return 1;

/// code from C# calling application
namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        [DllImport("MyDLL.dll")]
        unsafe private static extern int Get_The_Material(byte[] TradeName);


unsafe private void btnMyDLL_Click(object sender, EventArgs e)
        {
              byte[] TradeName;
                TradeName = new byte[50];
            Get_The_Material(TradeName);
…. Rest of code
	  }