Are you using WP-SimpleViewer (the dedicated SimpleViewer plugin for WordPress)?
If so, the plugin allows only one gallery per post. (A gallery sourced by Media Library images will display all images attached to the post so if you had two galleries in the same post, they would both display the same images.)

If you are not using WP-SimpleViewer but are embedding your galleries manually, then please ensure that you are embedding each gallery into a container with a unique id and that each gallery's embedding code uses a unique flashvars variable name.

If the notes above do not help, then please post the URL to your web page so that I can take a look at the problem for myself and hopefully help further. Thank you.

Thank you for providing the URLs to your web pages.
It looks like your problem may be due to trying to store the files for all three galleries in the same directory (your root directory).
You can do this but you would need to give each gallery's XML file a unique name (they cannot all be called 'gallery.xml' if they are stored in the same directory).
You would then point towards a specific XML file using a galleryURL in your gallery's embedding code.

For example, one gallery's embedding code might look like this:

<!--START SIMPLEVIEWER EMBED.-->
<script type="text/javascript" src="svcore/js/simpleviewer.js"></script>
<script type="text/javascript">
    var flashvars = {};
    flashvars.galleryURL = "first_gallery.xml";
    simpleviewer.ready(function () {
    simpleviewer.load("sv-container", "700", "680", "transparent", true, flashvars);
});
</script>
<div id="sv-container"></div>
<!-- END SIMPLEVIEWER EMBED -->

... and another gallery's embedding code (on a different page) might look like this:

<!--START SIMPLEVIEWER EMBED.-->
<script type="text/javascript" src="svcore/js/simpleviewer.js"></script>
<script type="text/javascript">
    var flashvars = {};
    flashvars.galleryURL = "second_gallery.xml";
    simpleviewer.ready(function () {
    simpleviewer.load("sv-container", "700", "680", "transparent", true, flashvars);
});
</script>
<div id="sv-container"></div>
<!-- END SIMPLEVIEWER EMBED -->

Alternatively, you could use the baseURL method of embedding as documented here.
This would allow you to keep each gallery in its own individual folder. You would then upload the complete gallery folders (not just the contents) to your web server and paste the baseURL embedding code into your web pages. It does not matter where on your web server you upload your gallery folders to as long as the two paths in the embedding code (the path to the 'simpleviewer.js' file and the baseURL itself, pointing towards the gallery folder) are correct.

I hope this helps.