程序老是会死掉

Question

程序运行一段时间老是会死掉。我找不到远因。麻烦各位指点下小弟。。谢谢。代码如下：
Thread tt = null;
        private void openFileDialog1_FileOk(object sender, CancelEventArgs e)
        {
            tt = new Thread(new ThreadStart(import));
            this.dgvNewHouse.Enabled = false;
            this.toolStrip1.Enabled = false;
            this.tsPages.Enabled = false;
            this.grp1.Enabled = false;
            this.panel3.Visible = true;
            this.progressBar1.Enabled = true;
            this.richTextBox1.Enabled = true;
            this.button1.Enabled = true;
            this.panel3.Enabled = true;
            tt.Start();
        }
        int errCount = 0;
        private void import() {
            int countNum = 1;
            ImportExportToExcel iete = new ImportExportToExcel();
            string fileName = "";            if (this.openFileDialog1.FileName.Trim() != "")
            {
                fileName = this.openFileDialog1.FileName;
            }
            else
            {
                return;
            }
            try
            {
                DataSet ds = iete.ImportFromExcel(fileName);
                this.progressBar1.Maximum = ds.Tables[0].Rows.Count;
                this.progressBar1.Value = 0;
                this.richTextBox1.Text = "";
                errCount = 0;
                Thread.CurrentThread.Join(50);
                for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
                {
                    try
                    {
                        Thread.Sleep(50);
                        this.progressBar1.Value += 1;
                        ConsolveHouseBean bean = new ConsolveHouseBean();
                        try
                        {
                            bean.CArea1 = float.Parse(ds.Tables[0].Rows[i]["安置面积"].ToString());
                        }
                        catch
                        {                        }
                        bean.CArea2 = float.Parse(ds.Tables[0].Rows[i]["另购面积"].ToString());
                        bean.CConsolveTime = ds.Tables[0].Rows[i]["安置时间"].ToString();
                        bean.CCountArea = float.Parse(ds.Tables[0].Rows[i]["总面积"].ToString());
                        int ccpid = 0;
                        DataSet dsNewPro = proBll.findAllPro(new ConsolveProject());
                        for (int j = 0; j < dsNewPro.Tables[0].Rows.Count; j++)
                        {
                            if (ds.Tables[0].Rows[i]["安置项目"].ToString() == dsNewPro.Tables[0].Rows[j]["cPName"].ToString())
                            {
                                ccpid = Int32.Parse(dsNewPro.Tables[0].Rows[j]["cPId"].ToString());
                            }
                        }
                        bean.CCPId = ccpid;
                        bean.CHouseNumber = ds.Tables[0].Rows[i]["房间号码"].ToString();
                        bean.CMember = ds.Tables[0].Rows[i]["成员名称"].ToString();
                        bean.CMemberCount = Int32.Parse(ds.Tables[0].Rows[i]["成员数"].ToString());
                        bean.CNote = ds.Tables[0].Rows[i]["备注"].ToString();
                        bean.CUserIDCard = ds.Tables[0].Rows[i]["户主身份证"].ToString();
                        bean.CUserName = ds.Tables[0].Rows[i]["户主名称"].ToString();
                        nhBll.add(bean);
                        this.richTextBox1.AppendText("成功插入第" + (i + 1) + "条数据. \r\n");
                        this.richTextBox1.ScrollToCaret();
                        countNum++;
                    }
                    catch {
                        this.richTextBox1.AppendText("准备插入第" + (i + 1) + "条数据失败，可能是数据的格式不完整导致. \r\n");
                        this.richTextBox1.ScrollToCaret();
                        errCount++;
                    }
                }
                this.richTextBox1.AppendText("导入完成");
                this.button1.Text = "完成";
            }
            catch(Exception eee)
            {
                MessageBox.Show(eee.Message.ToString());
                MessageBox.Show("数据异常，请检查导入文件的数据");
                return;
            }
        }