The photo-gallery works all fine,
except for pictures are not willing to be downloaded (showdownloadbutton is active) and after OK no file is downloaded.

embeded code in joomla:
-------------
<script type="text/javascript" src="/svcore/js/simpleviewer.js"></script>
<script type="text/javascript">// <![CDATA[
var flashvars = {}; flashvars.baseURL = "/-__g/myFolder/";
var params = {};params.wmode = "transparent";
simpleviewer.ready(function () {simpleviewer.load("glry", "920", "850", "222222", true, flashvars, params);});
// ]]></script>
<div ... ect.

gallery.xml
-------------
<?xml version="1.0" encoding="UTF-8"?>
<simpleviewergallery

    title="my title"
    maxImageWidth="1400"
    maxImageHeight="1200"
    useFlickr="false"
    imagePath="photos/"
    thumbPath="thumbnails/"
    showDownloadButton="true"
....
>
  <image imageURL="photos/001_DSC3644.jpg"
    thumbURL="thumbnails/001_DSC3644.jpg"
    linkURL="photos/001_DSC3644.jpg"
    linkTarget="_blank">
    <caption><![CDATA[© me, 2012]]></caption>
  </image>
...
</simpleviewergallery>
(over 150 photos in total)

.htaccess (almost standard joomla)
-------------
RewriteEngine On

# Block out any script trying to base64_encode data within the URL.
RewriteCond %{QUERY_STRING} base64_encode[^(]*\([^)]*\) [OR]
# Block out any script that includes a <script> tag in URL.
RewriteCond %{QUERY_STRING} (<|%3C)([^s]*s)+cript.*(>|%3E) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL.
RewriteCond %{QUERY_STRING} GLOBALS(=|\[|\%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL.
RewriteCond %{QUERY_STRING} _REQUEST(=|\[|\%[0-9A-Z]{0,2})
# Return 403 Forbidden header and show the content of the root homepage
RewriteRule .* index.php [F]

RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
#
# If the requested path and file is not /index.php and the request
# has not already been internally rewritten to the index.php script
RewriteCond %{REQUEST_URI} !^/index\.php
# and the request is for something within the component folder,
# or for the site root, or for an extensionless URL, or the
# requested URL ends with one of the listed extensions
        RewriteCond %{REQUEST_URI} /component/|(/[^.]*|\.(php|html?|feed|pdf|vcf|raw|jpg|xml|txt))$ [NC]
# and the requested path and file doesn't directly match a physical file
RewriteCond %{REQUEST_FILENAME} !-f
# and the requested path and file doesn't directly match a physical folder
RewriteCond %{REQUEST_FILENAME} !-d
# internally rewrite the request to the index.php script
RewriteRule .* index.php [L]
-----
I've also tried to change the line deleting |jpg|:
        RewriteCond %{REQUEST_URI} /component/|(/[^.]*|\.(php|html?|feed|pdf|vcf|raw|xml|txt))$ [NC]
- did not help