error occurred while downloading the update

I read the other topics on the issue but didn't find anything to solve my problem. When using Feeder to create my appcast, I can click on the link in the enclosure and it will download the new version fine. Or, I can copy the link in the enclosure tag, paste it in a browser and the file will be downloaded right away. But when clicking the "Download" button in the update dialog, I get these errors in the console:

Sparkle Error: An error occurred while downloading the update. Please try again later.
Sparkle Error (continued): The operation couldn’t be completed. (NSURLErrorDomain error -1100.)

NSURLErrorDomain -1100 is "File not found" error. But, the files seems to be there since I can download it from Feeder and the browser.

My appcast is currently hosted internally at the company where I work so I can't provide a link but I can provide the content of my appcast here:

<?xml version="1.0" encoding="utf-8"?>
<rss xmlns:atom="http://www.w3.org/2005/Atom" xmlns:sparkle="http://www.andymatuschak.org/xml-namespaces/sparkle" version="2.0">
    <channel>
        <title>PL Reader</title>
        <link>http://www.plasticlogic.com</link>
        <description>Feed to Macintosh PL Reader updates</description>
        <generator>Feeder 2.0.6(1186) http://reinventedsoftware.com/feeder/</generator>
        <docs>http://blogs.law.harvard.edu/tech/rss</docs>
        <language>en</language>
        <copyright>©2009 Plastic Logic</copyright>
        <managingEditor><email address hidden></managingEditor>
        <webMaster><email address hidden></webMaster>
        <pubDate>Fri, 25 Sep 2009 13:08:16 -0700</pubDate>
        <lastBuildDate>Fri, 25 Sep 2009 13:08:16 -0700</lastBuildDate>
        <atom:link href="http://wiki/download/PLReaderAppcast.xml" rel="self" type="application/rss+xml"/>
        <item>
            <title>PL Reader build 137 Available</title>
            <description><![CDATA[<p>-Add auto-update feature (ZEUS-871)
<br />-Fixes "Send to Reader" item not working (ZEUS-1402)</p>]]></description>
            <pubDate>Wed, 23 Sep 2009 13:13:01 -0700</pubDate>
            <enclosure url="http://builds/view/Builds/job/Mac_neocompanion_continuous/lastSuccessfulBuild/artifact/Macintosh/Neo%20Companion/build/Release/PL%20Reader.app//*zip*/PL%20Reader.app.zip" length="1719042" type="application/octet-stream" sparkle:version="137" sparkle:shortVersionString="1.0a12" sparkle:dsaSignature="MC0CFGSVKfJaSYWkWbnH8XKHKQyAXPFkAhUAjKtDkrBaNRzxnnTtgX1ofVGNPIM="/>
        </item>
    </channel>
</rss>

So, what's the problem?

Thanks in advance!