ok, nn ti preoccupare..tutto si risolve...
guardiamo cosa potrebbe interessare il componente che hai scaricato e cosa generare l'errore..
hai modificato il file htaccess x caso?
nella guida dice di settare così il .htaccess
##
# @version $Id: htaccess.txt 2368 2006-02-14 17:40:02Z stingrey $
# @package Joomla
# @copyright Copyright (C) 2005 Open Source Matters. All rights reserved.
# @license http://www.gnu.org/copyleft/gpl.html GNU/GPL
# Joomla! is Free Software
##
#####################################################
# READ THIS COMPLETELY IF YOU CHOOSE TO USE THIS FILE
#
# The line just below this section: 'Options FollowSymLinks' may cause problems
# with some server configurations. It is required for use of mod_rewrite, but may already
# be set by your server administrator in a way that dissallows changing it in
# your .htaccess file. If using it causes your server to error out, comment it out (add # to
# beginning of line), reload your site in your browser and test your sef url's. If they work,
# it has been set by your server administrator and you do not need it set here.
#
# Only use one of the two SEF sections that follow. Lines that can be uncommented
# (and thus used) have only one #. Lines with two #'s should not be uncommented
# In the section that you don't use, all lines should start with #
#
# For Standard SEF, use the standard SEF section. You can comment out
# all of the RewriteCond lines and reduce your server's load if you
# don't have directories in your root named 'component' or 'content'
#
# If you are using a 3rd Party SEF or the Core SEF solution
# uncomment all of the lines in the '3rd Party or Core SEF' section
#
#####################################################
##### SOLVING PROBLEMS WITH COMPONENT URL's that don't work #####
# SPECIAL NOTE FOR SMF USERS WHEN SMF IS INTEGRATED AND BRIDGED
# OR ANY SITUATION WHERE A COMPONENT's URL's AREN't WORKING
#
# In both the 'Standard SEF', and '3rd Party or Core SEF' sections the line:
# RewriteCond %{REQUEST_URI} ^(/component/option,com) [NC,OR] ##optional - see notes##
# May need to be uncommented. If you are running your Joomla/Mambo from
# a subdirectory the name of the subdirectory will need to be inserted into this
# line. For example, if your Joomla/Mambo is in a subdirectory called '/test/',
# change this:
# RewriteCond %{REQUEST_URI} ^(/component/option,com) [NC,OR] ##optional - see notes##
# to this:
# RewriteCond %{REQUEST_URI} ^(/test/component/option,com) [NC,OR] ##optional - see notes##
#
#####################################################
## Can be commented out if causes errors, see notes above.
Options FollowSymLinks
#
# mod_rewrite in use
RewriteEngine On
# Uncomment following line if your webserver's URL
# is not directly related to physical file paths.
# Update Your Joomla/MamboDirectory (just / for root)
# RewriteBase /
########## Begin Standard SEF Section
## ALL (RewriteCond) lines in this section are only required if you actually
## have directories named 'content' or 'component' on your server
## If you do not have directories with these names, comment them out.
#
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteCond %{REQUEST_URI} ^(/component/option,com) [NC,OR] ##optional - see notes##
#RewriteCond %{REQUEST_URI} (/|\.htm|\.php|\.html|/[^.]*)$ [NC]
#RewriteRule ^(content/|component/) index.php
#
########## End Standard SEF Section
########## Begin 3rd Party or Core SEF Section
#
#RewriteCond %{REQUEST_URI} ^(/component/option,com) [NC,OR] ##optional - see notes##
RewriteCond %{REQUEST_URI} (/|\.htm|\.php|\.html|/[^.]*)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*) index.php
#
########## End 3rd Party or Core SEF Section
