System.IO.IOException: There is a time and/or date difference between the client and server
<p>I'm trying to copy a file, using System.IO.File.Copy() from a network location, to a client.
This has been working for a long time, but now, all of a sudden, clients are getting this error:</p>

<blockquote>
  <p>System.IO.IOException: There is a time and/or date difference between
  the client and server.</p>
</blockquote>

<p>I've googled around, but haven't been able to find anything related to C# or .Net.</p>
