Problem sa zatvaranjem forme

Code:
public partial class BalloonAdd : DevComponents.DotNetBar.Balloon
    {
        private string dt;
        private OleDbDataReader dReader;
        private OleDbCommand selectCommand;
        private string[] arrayRJ = new string[50];

        public BalloonAdd()
        {
            InitializeComponent();
        }

        private void BalloonAdd_Deactivate(object sender, EventArgs e)
        {
            this.Opacity = .75;
        }

        private void BalloonAdd_Activated(object sender, EventArgs e)
        {
            this.Opacity = 1;
        }

        private void buttonDodaj_Click(object sender, EventArgs e)
        {
            
            if (this.Owner != null)
            {
                if (comboBox1.Text == String.Empty || textBox1.Text == String.Empty || comboBox1.Text.Equals("Prezime i ime ...") || textBox1.Text.Equals("Zadatak..."))
                { MessageBox.Show("Niste selektovali radnika ili je polje \"Zadatak\" prazno!", "Dodaj...", MessageBoxButtons.OK, MessageBoxIcon.Information); }
                else
                {
                    Cursor.Current = AdvancedCursors.Create("aero_busy.ani");

                    string prezimeime = comboBox1.Text;
                    string prezime = "";
                    string ime = "";

                    string[] sp = prezimeime.Split(" ".ToCharArray(), 2);

                    if (sp.Length > 1)
                    {
                        prezime = sp[0].Trim();
                        ime = sp[1].Trim();
                    }

                    if (textBox2.Text == String.Empty || textBox2.Text == "Kljucna rijec...")
                        textBox2.Text = "";

                    int comboIndex = comboBox1.SelectedIndex;

                    ((frmMain)this.Owner).AddToActiveZDocument(prezime, ime, arrayRJ[comboIndex], textBox1.Text, maskedTextBox1.Text, textBox2.Text,"");

                    Cursor.Current = Cursors.Default;

                    this.Close();
                }
            }
        }

        private void comboBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (Char.IsControl(e.KeyChar))
            {
                if (e.KeyChar == (char)Keys.Return)
                    textBox1.Focus();

                return;
            }

            ComboBox comboBox = (ComboBox)sender;
            comboBox.DroppedDown = true;

            string s = comboBox.Text.Substring(0, comboBox.SelectionStart) + e.KeyChar;
            int i = comboBox.FindStringExact(s);

            if (i == -1)
                i = comboBox.FindString(s);

            if (i == -1)
                return;

            comboBox.SelectedIndex = i;
            comboBox.SelectionStart = s.Length;
            comboBox.SelectionLength = comboBox.Text.Length - comboBox.SelectionStart;

            e.Handled = true;
        }

        private void BalloonAdd_Load(object sender, EventArgs e)
        {
            selectCommand = new OleDbCommand("select prezime,ime,rj from radnik order by prezime", clsConnection.CN);
            dReader = selectCommand.ExecuteReader();

            int i = 0;
            if (dReader.HasRows)
            {
                while (dReader.Read())
                {
                    comboBox1.Items.Add(dReader[0].ToString() + " " + dReader[1].ToString());
                    arrayRJ[i] = dReader[2].ToString();
                    i++;
                }
            }
            dReader.Close();

            Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("sr-SP-Latn");
            DateTime dateTime = DateTime.Now;
            dt = dateTime.ToString("dd.MM.yyyy hh:mm");
            maskedTextBox1.Text = dt;
        }

        private void maskedTextBox1_Enter(object sender, EventArgs e)
        {
            if (maskedTextBox1.Text != String.Empty)
            {
                //maskedTextBox1.ForeColor = Color.Yellow;
                //maskedTextBox1.BackColor = Color.DarkSlateGray;
                maskedTextBox1.Clear();
            }
        }

        private void maskedTextBox1_Leave(object sender, EventArgs e)
        {
            if (maskedTextBox1.Text == "  .  .       :")
                maskedTextBox1.Text = dt;
            
            //maskedTextBox1.ForeColor = Color.Black;
            //maskedTextBox1.BackColor = Color.White;
        }

        private void textBox2_Enter(object sender, EventArgs e)
        {
            //textBox2.ForeColor = Color.Yellow;
            //textBox2.BackColor = Color.DarkGray;
            textBox2.Clear();
        }

        private void textBox2_Leave(object sender, EventArgs e)
        {
            if (textBox2.Text == String.Empty)
                textBox2.Text = "Kljucna rijec...";


            //textBox2.ForeColor = Color.Black;
            //textBox2.BackColor = Color.White;
        }

        private void RadioCheckState(object sender, EventArgs e)
        {
            Cursor.Current = AdvancedCursors.Create("aero_busy.ani");

            if (radioButton1.Checked)
            {
                comboBox1.Items.Clear();

                dReader = selectCommand.ExecuteReader();

                int i = 0;
                if (dReader.HasRows)
                {
                    while (dReader.Read())
                    {
                        comboBox1.Items.Add(dReader[0].ToString() + " " + dReader[1].ToString());
                        arrayRJ[i] = dReader[2].ToString();
                        i++;
                    }
                }
                dReader.Close();
                comboBox1.Text = "Prezime i ime ...";
            }
            else
            {
                comboBox1.Items.Clear();

                dReader = selectCommand.ExecuteReader();

                int i = 0;
                if (dReader.HasRows)
                {
                    while (dReader.Read())
                    {
                        comboBox1.Items.Add(dReader[1].ToString() + " " + dReader[0].ToString());
                        arrayRJ[i] = dReader[2].ToString();
                        i++;
                    }
                }
                dReader.Close();
                comboBox1.Text = "Ime i prezime ...";
            }

            comboBox1.Focus();

            Cursor.Current = Cursors.Default;
        }
    }