title: Adding to/Delete from zip file can't find temp files
body: <p>My program lets users add files to a zip file one upload at a time.  The first upload creates a zip file, and subsequent uploads add to the created file.  It also displays a list of all the files in the zip file, and lets users delete individual files.</p>
  
  <p>I use SharpZipLib and this works perfectly on my local computer, but once I uploaded it to the server it started crashing at CommitUpdate()</p>
  
  <p>The original upload that creates the zip file is fine, but adding to the zip file, or deleting from it gives:</p>
  
  <p>Could not find file 'W:\MyZipFile.zip.151.tmp'. </p>
  
  <p>If I leave the window alone for a while, I can delete one file or add one file before the error starts again.</p>
  
  <p>My add file method:  </p>
  
  <pre><code>ZipFile z = null;
  if (System.IO.File.Exists(filePath + zipFilename))
       z = new ZipFile(File.OpenRead(filePath + zipFilename));
  else
       z = ZipFile.Create(filePath + zipFilename);
  z.BeginUpdate();
  z.Add(filePath + filename, filename);
  z.CommitUpdate();
  z.Close();
  </code></pre>