Win7 CSV Edit programm not working under Win Server 2008

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C#

Hello everybody, i got a little Problem.

i programmed a little C# app to edit some .csv files (filter linebreaks and ending lines) to make an import into another system easier.
The programm works fine on 5 machines all win7 without any problems and completes the task within 30 seconds, but as soon as i try to run it on a win 2008 R2 server it freezes. here is the code:

The filepath are read through a txt file to make it more flexible in case the source or destination folders change. As well as a txt file for the line that need to be removed at the end of the csv.


Main form (using a timer)

private void timer1_Tick(object sender, EventArgs e)
       {
           try
           {
               //todo  Read Configfile
               string sourcePath = Application.StartupPath + "\\SourceFolder.txt";
               string targetPath = Application.StartupPath + "\\TargetFolder.txt";
               srSource = new StreamReader(sourcePath);
               srTarget = new StreamReader(targetPath);
               string target="";
               while (!srTarget.EndOfStream)
               {
                   target = srTarget.ReadLine();
               }
               //testing
               writeError(System.DateTime.Now.ToString() + " ->Starting write Target: " + target);
               // TEST IS OK. File is written
               while (!srSource.EndOfStream)
               {
                   string line = srSource.ReadLine();
                   string[] filePaths = Directory.GetFiles(line, "*.csv");
                   foreach (string file in filePaths)
                   {
                       try
                       {
                           FileInfo fi = new FileInfo(file);
                           ChristmasCards ccrd = new ChristmasCards(Application.StartupPath + "\\ConfigEndings.txt"); // Conditions for ending lines (each line is a line that needs to be removed)
                           if (ccrd.OK)
                           {
                               DirectoryInfo dir = new DirectoryInfo(target);
                               if (!dir.Exists)
                               {
                                   dir.Create();
                               }
                               FileInfo destfi = new FileInfo(target+"\\" + fi.Name);
                               writeError(System.DateTime.Now.ToString() + " ->Readinfo Target " + target+"\\"+fi.Name); // write ok!

                               if (destfi.Exists)
                               {
                                   destfi.Delete();
                               }
                               //do process
                               string result = ccrd.ReadCSV(file, target + "\\" + fi.Name);

                               //Check if everything saved ok
                               if (result == "OK")
                                   writeError(System.DateTime.Now.ToString() + " -> " +"\r\nFile Saved as: " + target + "\\" + fi.Name);
                               else
                                  writeError(System.DateTime.Now.ToString() + " -> " +"\r\nError File saving: " + result);
                           }
                           else
                           {
                               writeError(System.DateTime.Now.ToString() + " -> " + "\r\nError Configfile not readable");
                               srSource.Close();
                           }
                       }
                       catch (Exception ex)
                       {
                           writeError(System.DateTime.Now.ToString() + " -> " + "\r\nError:" + ex.Message);
                           srSource.Close();
                       }
                   }
               }
               srSource.Close();
               srTarget.Close();
           }
           catch (Exception ex)
           {
               writeError(System.DateTime.Now.ToString() + " -> " + "\r\nError:" + ex.Message);
           }
           finally
           {
               this.Close();
               Application.Exit();
           }
       }
       private void writeError(string message)
       {
           StreamWriter errorwriter = new StreamWriter(Application.StartupPath + "\\Errors.txt", true, System.Text.Encoding.Default);
           errorwriter.WriteLine(System.DateTime.Now.ToString()+" -> "+ message);
           errorwriter.Close();
       }

Christmas card class function

        StreamReader conditionsreader;
        StreamReader csv;
        StreamWriter csvwrite;
        bool ok = false;
        ArrayList cond = new ArrayList();
        

        #region constructor
        public ChristmasCards(string configfile)
        {
            try
            {
                conditionsreader = new StreamReader(configfile);
                while (!conditionsreader.EndOfStream)
                {
                    cond.Add(conditionsreader.ReadLine());
                }
                conditionsreader.Close();
                ok = true;
            }
            catch (Exception ex)
            {
                ok = false;
            }
        }
public string ReadCSV(string filename, string destfilename)
        {
            try
            {
                bool nextline = false;
                bool write = true;
                // open the file "data.csv" which is a CSV file with headers
                csv = new StreamReader(filename, System.Text.Encoding.Default);                
                csvwrite = new StreamWriter(destfilename, true, System.Text.Encoding.Default);
                while (!csv.EndOfStream)
                {
                    // remove line breaks
                    string line = csv.ReadLine();
                    if (!line.EndsWith("\""))
                    {
                        nextline = true;
                        while (nextline)
                        {
                            line += csv.ReadLine();
                            if (line.EndsWith("\""))
                                nextline = false;
                        }
                    }
                    //filter ending lines

                    foreach (string s in cond)
                    {
                        if (line.Contains(s))
                        {
                            line = "";
                            write = false;
                        }
                    }
                    //TODO Write the line
                    if (write)
                        csvwrite.WriteLine(line);
                }
                //close streams
                csv.Close();
                csvwrite.Close();
                return "OK";
            }
            catch (Exception ex)
            {
                csvwrite.Close();
                csv.Close();
                return ex.Message;
            }
        }

The program on the server reaches the point where it creates the first csv with 0 bytes but then it freezes. and its already running as Administrator. any ideas?