please post the url to the gallery.

Looks like your flash drop-down menu is taking the mouse clicks. AFAIK it's not possible to overlay one swf over another without issues. You could move the thumbnails to the right of your gallery.

I am having the same issue with firefox...although I am pretty sure its not the same cause.  When the window is resized (smaller) I cannot click on the top thumbnail. Here is the url: http://www.classicrealestate.com/listin … ?MLS_NUM=3

Thanks Steven for your reply and your help.  I set the background to a color but it made no difference.  I made sure to clear the cache but the problem still persists in Firefox.

Try again, deselecting the 'Backgnd transparent' checkbox on the 'Customize' page and then click 'Update'.
I have tested the functionality of this in the latest version of svManager (v1.7.7) and it works correctly for me.

I've just validated your page at the W3C Markup Validation Service and noticed that the code for the gallery (the <iframe>) is outside the closing </body> and </html> tags.
It should be inside these tags.
Also, there are other errors on the page that should be fixed in order for the page to validate and be displayed with greater consistency when viewed in different browsers.

Try setting the 'wmode' param to 'opaque' instead of 'transparent'.
Keep the 'Backgnd Transparent' checkbox deselected in svManager (ie use a color for the background rather than set it to be transparent) and edit the file: http://www.classicrealestate.com/listin … /index.php manually.
Download the file from your web server, open it in a plain text editor and change the following code in the file before reuploading it.
Change:

    <!--START SIMPLEVIEWER EMBED -->
    <script type="text/javascript" src="svcore/js/simpleviewer.js"></script>
    <script type="text/javascript">
      var flashvars = {};
      flashvars.galleryURL = "gallery.xml?nocache=<?php echo rand(); ?>";
      simpleviewer.ready(function () {
        simpleviewer.load(
          'sv-container',
          <?php print $galleryWidth; ?>,
          <?php print $galleryHeight; ?>,
          <?php print $backgroundColor; ?>,
          <?php print $useFlash; ?>,
          <?php print $flashVars; ?>,
          <?php print $params; ?>,
          <?php print $attributes; ?>,
          <?php print $useColorCorrection; ?>
          );
      });
    </script>
    <div id="sv-container"></div>
    <!--END SIMPLEVIEWER EMBED -->

... to:

    <!--START SIMPLEVIEWER EMBED -->
    <script type="text/javascript" src="svcore/js/simpleviewer.js"></script>
    <script type="text/javascript">
      var flashvars = {};
      flashvars.galleryURL = "gallery.xml?nocache=<?php echo rand(); ?>";
      var params = {};
      params.wmode = "opaque";
      simpleviewer.ready(function () {
        simpleviewer.load(
          'sv-container',
          <?php print $galleryWidth; ?>,
          <?php print $galleryHeight; ?>,
          <?php print $backgroundColor; ?>,
          <?php print $useFlash; ?>,
          <?php print $flashVars; ?>,
          params,
          <?php print $attributes; ?>,
          <?php print $useColorCorrection; ?>
          );
      });
    </script>
    <div id="sv-container"></div>
    <!--END SIMPLEVIEWER EMBED -->

Try giving your menu a greater z-index than your gallery to force it to the front.
Change:

<div class="menu">

... to:

<div class="menu" style="z-index: 99;">

And change:

<div class="center">

... to:

<div class="center" style="z-index: 98;">

In doing this, you should also be able to revert the gallery's index.php page back to the way it was before and have your background as either transparent or a color.