End Sub after closing a windows for causes Excel to crash, why?

The following sub in my com-addin does not cause any problems:

Private Sub MonthCalendar1_DateChanged(sender As Object, e As Windows.Forms.DateRangeEventArgs) Handles MonthCalendar1.DateChanged
        Dim ExcelApp As Excel.Application = CType(AddinExpress.MSO.ADXAddinModule.CurrentInstance, AddinModule).ExcelApp
        ExcelApp.ActiveCell.Value = MonthCalendar1.SelectionStart.Date
    End Sub

The following sub however, where I have added a Me.Close() statement, causes Excel to crash. What might the reason be?

Private Sub MonthCalendar1_DateChanged(sender As Object, e As Windows.Forms.DateRangeEventArgs) Handles MonthCalendar1.DateChanged
        Dim ExcelApp As Excel.Application = CType(AddinExpress.MSO.ADXAddinModule.CurrentInstance, AddinModule).ExcelApp
        ExcelApp.ActiveCell.Value = MonthCalendar1.SelectionStart.Date
        Me.Close()
    End Sub

EDIT: Maybe my code triggers some other event in my code to execute and that causes Excel to crash? Is it possible to pause execution at the start of any event? Since I don't know which event might be called, I would't know where to add a breakpoint.