Steps to reproduce: - Create a form with RadDock on it - Use the following code in another form: Using frm As New FormWithDock() frm.ShowDialog() End Using - Close the dialog (FormWithDock) -> exception is thrown WORKAROUND - dispose the dock on form closing: Protected Overrides Sub OnClosing(e As System.ComponentModel.CancelEventArgs) RadDock1.Dispose() MyBase.OnClosing(e) End Sub
I also found this and can sometimes manifest itself as the following exception at System.Drawing.Region.GetHrgn(Graphics g) at System.Windows.Forms.Control.GetHRgn(Region region) at System.Windows.Forms.Control.OnHandleCreated(EventArgs e)