Installation: Generate Cruft-Free URLs not working

Hi;

new installation of Plogger (Version 1.0 RC1). Everything works fine except for the *Generate Cruft-Free URLs* option. I check the box, save, and it's unckecked again. The .htaccess file has been modified, though. Here's what's in there:
--------------------------------------------
# BEGIN Plogger
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteBase /photos
RewriteCond %{REQUEST_URI} !(\.|/$)
RewriteRule ^.*$ http://www.mysite.org%{REQUEST_URI}/ [R=301,L]
RewriteCond %{HTTP_HOST} !^www [NC]
RewriteRule ^(.*)$ http://www.mysite.org/photos/$1 [R=301,L]
RewriteCond %{REQUEST_FILENAME} -d [OR]
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^.*$ - [S=2]
RewriteRule feed/$ plog-rss.php?path=%{REQUEST_URI} [L]
RewriteRule ^.*$ index.php?path=%{REQUEST_URI} [L]
</IfModule>
# END Plogger
---------------------------------

Can anybody spot a problem?

Thanks, ciao

Massimo