500 internal server error at wp-admin/tools.php

Hello,
when I click in WP 2.7.1’s tools, I get this:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, root@jupiter.net-server.de and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

I’ve checked the folder, the file is there. What could be wrong? There’s only one .htaccess in wp’s root folder with the following content:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress
# BEGIN Url Rewrite section
# (Automatically generated. Do not edit this section)
<IfModule mod_rewrite.c>
RewriteEngine On

RewriteBase /wp/

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d [OR]
RewriteCond %{REQUEST_FILENAME} gallery\_remote2\.php
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . – [L]

RewriteCond %{THE_REQUEST} \ /wp/slideshow/slideshow.html(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=slideshow.Slideshow [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/gallery/(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=core.ShowItem [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/admin/(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=core.SiteAdmin [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/comments/view/([0-9]+).html(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=core.ItemAdmin&g2_subView=comment.ShowComments&g2_itemId=%1 [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/comments/add/([0-9]+).html(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=core.ItemAdmin&g2_subView=comment.AddComment&g2_itemId=%1 [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/slideshow/([^?]+)/slideshow.html(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=slideshow.Slideshow&g2_path=%1 [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/download/([0-9]+)-([0-9]+)/([^\/]+)(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=%1&g2_serialNumber=%2 [QSA,L]

RewriteCond %{THE_REQUEST} \ /wp/gallery/([^?]+)(\?.|\ .)
RewriteCond %{REQUEST_FILENAME} !wp-gallery2\.php
RewriteRule . /wp/wp-gallery2.php?g2_view=core.ShowItem&g2_path=%1 [QSA,L]

</IfModule>

# END Url Rewrite section

WP Gallery2 is not an active plugin btw. What happens if I just delete the file?
best regards,

GS