Installation Erweiterung funktioniert bei 3.4.8 nicht - jedoch bei 2.5 schon

Warnung
JInstaller: :Install: Die Joomla!-XML-Installationsdatei konnte nicht gefunden werden.

Fehler
Der Pfad führt zu keinem gültigen Paket!
Es kann kein Installationspaket gefunden werden!

Kann mir jemand helfen, woran es liegen könnte (die xml datei ist vorhanden, und hat auch den richtigen namen).
Vielen Dank!!!!!

anbei der xml code:
<?xml version="1.0" encoding="utf-8"?>
<install type="module" version="1.5.0">
<!-- Name of the Module -->
<name>TSSlider</name>

<!-- Name of the Author -->
<author>Templatesquare</author>

<!-- Version Date of the Module -->
<creationDate>2012-03-14</creationDate>

<!-- Copyright information -->
<copyright>All rights reserved by Templatesquare 2012.</copyright>

<!-- License Information -->
<license>GPL 2.0</license>

<!-- Author's email address -->
<authorEmail>support@templatesquare.com</authorEmail>

<!-- Author's website -->
<authorUrl>www.templatesquare.com</authorUrl>

<!-- Module version number -->
<version>1.0.0</version>

<!-- Description of what the module does -->
<description>Provides a slider for templatesquare themes</description>

<!-- Listing of all files that should be installed for the module to function -->
<files>
<!-- The "module" attribute signifies that this is the main controller file -->
<filename module="mod_tsslider">mod_tsslider.php</filename>
<filename>index.html</filename>
<filename>helper.php</filename>
<folder>languages</folder>
<folder>tmpl</folder>
</files>

<languages folder="languages">
<!-- Any language files included with the module -->
<language tag="en-GB">en-GB/en-GB.mod_tsslider.ini</language>
</languages>

<!-- Optional parameters -->
<config>
<fields name="params">
<fieldset name="advanced">
<!-- parameter to allow placement of a module class suffix for the module table / xhtml display -->
<field name="moduleclass_sfx" type="text" default="" label="Module Class Suffix" description="PARAMMODULECLASSSUFFIX" />

<!-- just gives us a little room between the previous parameter and the next -->
<field name="@spacer" type="spacer" default="" label="" description="" />

<field name="tsslider_sliderid" type="text" default="" filter="integer" label="TSSLIDER_SLIDER_ID_LABEL" description="TSSLIDER_SLIDER_ID_DESC" />
<field name="tsslider_orderby" type="list" default="ASC" label="TSSLIDER_ORDERBY_LABEL" description="TSSLIDER_ORDERBY_DESC">
<option value="ASC">Ascending</option>
<option value="DESC">Descending</option>
</field>
</fieldset>
</fields>
</config>
</install>