DotNetZip and CheckZip

Question

I've tried to use CheckZip in DotNetZip to test about 22.000 zip files, and it doesn't report any errors. WinRAR however reports "archive is corrupted" for a number of these files, so I wonder what's going on here, and if I've implemented CheckZip correctly. If I rename a text file to test.zip and check it I get a "test.zip is not a valid zip file" from DotNetZip so it looks like it's basically working though. Code looks like this:

 public static bool CheckZip(string zipFileName)
        {
            try
            {
                return ZipFile.CheckZip(zipFileName);
            }
            catch (Exception e)
            {
                MessageBox.Show(e.ToString());
                return false;
            }
        }

UPDATE: found a simple solution here, using SharpZipLib instead. Works fine.