sparkle dsaSignature not working on Snow Leopard

I'm using the latest spakle framework 1.5b6

when I create a dsa signature for a zip file using the provided ruby tools, the output for my signature is:
ruby sign_update.rb ~/projects/atvms/atvms101.zip dsa_priv.pem
MEQCIDDzykynzudIPxugWknQYfMZ4YKzqtgnCTJ1Bd6JAqfyAiBVr7fVNDt+Xuhj
FEYbsQ401aZ6dFsbjZwI6g5Q3c7EcQ==

adding this to the AppCast.xml produces an "The Update is improperly signed" error...

<?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>ATVApps.com - ATVMediaServer</title>
        <link>http://www.atvapps.com/downloads/updates/latest_atvms.xml</link>
        <description>Most recent changes with links to updates.</description>
        <language>en</language>
        <item>
        <pubDate>Tue, 28 Sep 2010 23:28:41 -0400</pubDate>
        <lastBuildDate>Tue, 28 Sep 2010 23:28:41 -0400</lastBuildDate>
            <title>Version 1.0.1</title>
            <pubDate>Tue, 28 Sep 2010 23:27:33 -0400</pubDate>
            <enclosure url="http://www.atvapps.com/downloads/updates/atvms101.zip"
            length="597789"
            type="application/zip"
            sparkle:version="1.0.1"
            sparkle:dsaSignature="MEQCIDDzykynzudIPxugWknQYfMZ4YKzqtgnCTJ1Bd6JAqfyAiBVr7fVNDt+Xuhj
FEYbsQ401aZ6dFsbjZwI6g5Q3c7EcQ=="/>
           <sparkle:releaseNotesLink>http://www.atvapps.com/downloads/updates/atvms101.html</sparkle:releaseNotesLink>
        </item>
    </channel>
</rss>

Please help Andy, your tool is awesome but I cannot trigger an update.

cheers
Ron