[ZenCart] Errore 500 per admin

Salve,
ho installato zenCart 1.39 ITA e adesso se voglio accedere come admin mi da l'errore 500. Ho temporaneamente rinominato .htaccess come descritto qui e mi fa accedere. Visto che anche altri utilizzano zenCart volevo sapere come avete fatto per farlo funzionare senza disabilitare .htaccess..?
Grazie mille in anticipo

questo è il file .htaccess

#
# @copyright Copyright 2003-2010 Zen Cart Development Team
# @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
# @version $Id: .htaccess 16111 2010-04-29 22:39:02Z drbyte $
#
# This is used with Apache WebServers
#
# The following blocks direct HTTP requests to all filetypes in this directory recursively, except certain approved 

exceptions
# It also prevents the ability of any scripts to run. No type of script, be it PHP, PERL or whatever, can normally 

be executed if ExecCGI is disabled.
# Will also prevent people from seeing what is in the dir. and any sub-directories
#
# For this to work, you must include either 'All' or at least: 'Limit' and 'Indexes' parameters to the 

AllowOverride configuration in your apache/conf/httpd.conf file.
# Additionally, if you want the added protection offered by the OPTIONS directive below, you'll need to add 

'Options' to the AllowOverride list, if 'All' is not specified. 
# Example:
#<Directory "/usr/local/apache/htdocs">
#  AllowOverride Limit Options Indexes
#</Directory>
###############################
DirectoryIndex index.php


# deny *everything*
<FilesMatch ".*\..*">
  Order Allow,Deny
  Deny from all
</FilesMatch>

# but now allow just *certain* necessary files:
<FilesMatch "(^$|^favicon.ico$|.*\.(php|js|css|jpg|gif|png)$)">
  Order Allow,Deny
  Allow from all
</FilesMatch>

IndexIgnore */*


# The following makes adjustments to the SSL protocol for Internet Explorer browsers
<IfModule mod_setenvif.c>
  <IfDefine SSL>
    SetEnvIf User-Agent ".*MSIE.*" \
             nokeepalive ssl-unclean-shutdown \
             downgrade-1.0 force-response-1.0
  </IfDefine>
</IfModule>

# Fix certain PHP values

#<IfModule mod_php4.c>
#  php_value session.use_trans_sid 0
#  php_value register_globals 1
#</IfModule>

# to turn off register_globals
# php_value register_globals 0

#turn off X-PHP-Originating-Script header when sending emails from admin
#uncomment to activate:
# php_flag mail.add_x_header Off

anche a me lo stesso problema in installazione....