File Locking/Acccess help when copying and deleteing

When using the FileInfo object I am trying to copy files from one folder to another. After the copy process is complete, I delete the file in the original folder.  After viewing the logs I see this error every once in awhile.

  The process cannot access the file [filename] because it is being used by another process

I have tried numerous pieces of code (GC.collect, fi.refresh, checking for the file being locked, etc ...) and I still get this error and even more frequently.  Here is some of the code.  The project is a windows service.

private void fsw_Watcher_Changed(object sender, System.IO.FileSystemEventArgs e)
            {
                  
                  FileInfo fi = new FileInfo(e.FullPath);      
                  fi.Refresh();
                  if(!fi.Exists) return;      

                  try
                  {
                        string trans_id = this.MakeTransactionID();                                                
                        this.LogReceiptOfFile(fi.Name,trans_id);                  
                        
                        if(fi.Name!="heartbeat.csv")
                        {
                              fi.Refresh();
                              this.CopyToArchive(fi,trans_id);
                        }                        
                        fi.Refresh();
                        this.CopyToOut(fi,trans_id);      
                        fi.Refresh();
                        this.DeleteFromIn(fi,trans_id);
                  }
                  catch(Exception ex)
                  {
                        this.LogError("fsw_Watcher_Changed",ex);
                  }
                  finally
                  {
                        fi = null;
                        GC.Collect();
                  }
            }

            private void LogReceiptOfFile(string fileName,string trans_id)
            {
                  Log myLog = new Log(LOGPATH);
                  myLog.WriteToProcessLog(trans_id,1,"Received","MCGWare",fileName);
                  myLog = null;
            }

            private void LogError(string func,Exception ex)
            {
                  Log myLog = new Log(LOGPATH);
                  myLog.WriteLogMessage(func,ex.Message + "\n" + ex.StackTrace,1);
                  myLog = null;

                  EventLog elog = new EventLog();
                  elog.Source = "Application";
                  elog.Log = "Application";
                  elog.WriteEntry("Error reported in fsw_Watcher_Changed function. Read SDX log files for details.",
                        System.Diagnostics.EventLogEntryType.Error);      
                  elog = null;
            }

            private void CopyToArchive(FileInfo fi,string trans_id)
            {
                  Log myLog = new Log(this.processPath);
                  string fileName =
                        this.archivePath + "\\" +
                        this.MakeFileName(fi.Name.Replace(".csv",""));                  
                  try
                  {
                        fi.CopyTo(fileName,true);
                        myLog.WriteToProcessLog(trans_id,1,"Copy",fi.FullName,fileName);
                  }
                  catch(Exception ex)
                  {
                        this.LogError("CopyToArchive",ex);
                        myLog.WriteToProcessLog(trans_id,0,"Copy",fi.FullName,fileName);
                  }
                  finally
                  {
                        myLog = null;
                  }
            }

            private void CopyToOut(FileInfo fi,string trans_id)
            {
                  Log myLog = new Log(this.processPath);
                  string fileName = this.outPath + "\\" + fi.Name;
                  try
                  {
                        fi.CopyTo(fileName,true);
                        myLog.WriteToProcessLog(trans_id,1,"Copy",fi.FullName,fileName);
                  }
                  catch(Exception ex)
                  {
                        this.LogError("CopyToOut",ex);
                        myLog.WriteToProcessLog(trans_id,0,"Copy",fi.FullName,fileName);
                  }
                  finally
                  {
                        myLog = null;
                  }
            }

            private void DeleteFromIn(FileInfo fi,string trans_id)
            {
                  Log myLog = new Log(this.processPath);
                  try
                  {
                        fi.Delete();
                        myLog.WriteToProcessLog(trans_id,1,"Delete",fi.FullName,"");
                  }
                  catch(Exception ex)
                  {
                        this.LogError("DeleteFromIn",ex);
                        myLog.WriteToProcessLog(trans_id,0,"Delete",fi.FullName,"");
                  }
                  finally
                  {
                        myLog = null;
                  }
            }