Unhandled exception of type SqlServerCe.SqlCeException

Ved exekvering af programmet opstår følgende fejl:
"An unhandled exception of type 'System.Data.SqlServerCe.SqlCeException'
occurred in System.Data.SqlServerCe.dll"

og programmet stopper efterfølgende på linien:
adapter.Fill(dataSet)

Hvad gør jeg galt???

Public Class Form1
    Inherits System.Windows.Forms.Form
    Friend WithEvents DataGrid As System.Windows.Forms.DataGrid


    Private Const DATABASE As String = "Data Source=\My
Documents\ATdata.sdf; Password='r2d2'"
    Public Sub New()

        MyBase.New()

        InitializeComponent()

        Dim conn As SqlServerCe.SqlCeConnection = New
SqlServerCe.SqlCeConnection(DATABASE)

        Dim adapter As SqlServerCe.SqlCeDataAdapter = New
SqlServerCe.SqlCeDataAdapter
        Dim query As String = "SELECT Preis, TopLfd, TopVor, Bezeichnung,
Menge FROM MyTable"
        adapter.SelectCommand = New SqlServerCe.SqlCeCommand(query, conn)

        Dim dataSet As DataSet = New DataSet
        adapter.Fill(dataSet)

        DataGrid.DataSource = dataSet.Tables(0)


    End Sub

    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        MyBase.Dispose(disposing)
    End Sub

    Private Sub InitializeComponent()
        Me.DataGrid = New System.Windows.Forms.DataGrid
        '
        'DataGrid
        '
        Me.DataGrid.Size = New System.Drawing.Size(248, 264)
        Me.DataGrid.Text = "DataGrid"
        '
        'Form1
        '
        Me.ClientSize = New System.Drawing.Size(234, 295)
        Me.Controls.Add(Me.DataGrid)
        Me.Text = "SQL Server CE"
        Me.WindowState = System.Windows.Forms.FormWindowState.Maximized

    End Sub

    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub

#End Region

End Class