Linq to SQL Insert Problem

I have an entity class as below, but when I try to add a new row without specifying an EndDate, I get the error..

System.Data.SqlServerCe.SqlCeException: An overflow occurred while converting to datetime

If I add a row with an EndDate then all is fine.

<Table> _
Public Class Notes

    <Column(IsDbGenerated:=True, IsPrimaryKey:=True)> _
    Public Property Id() As Integer
        Get
            Return m_Id
        End Get
        Set(value As Integer)
            m_Id = value
        End Set
    End Property
    Private m_Id As Integer

    <Column> _
    Public Property StartDate() As System.Nullable(Of Date)
        Get
            Return m_StartDate
        End Get
        Set(value As System.Nullable(Of Date))
            m_StartDate = value
        End Set
    End Property
    Private m_StartDate As DateTime

    <Column(CanBeNull:=True)> _
    Public Property EndDate() As System.Nullable(Of Date)
        Get
            Return m_EndDate
        End Get
        Set(value As System.Nullable(Of Date))
            m_EndDate = value
        End Set
    End Property
    Private m_EndDate As DateTime

    <Column> _
    Public Property Note() As String
        Get
            Return m_Note
        End Get
        Set(value As String)
            m_Note = value
        End Set
    End Property
    Private m_Note As String
End Class

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