WordPress MU

I've set up a wordpress mu user installation for primary school children to blog at http://oliverquinlan.co.uk/rhs/blogs/

Most of it seems to work, the main page and individual blogs like this one are ok: http://oliverquinlan.co.uk/rhs/blogs/aaron12/

But when I click on an individual blog post ( http://oliverquinlan.co.uk/rhs/blogs/aaron12/2010/04/13/test-post/ )

Or a comments link ( http://oliverquinlan.co.uk/rhs/blogs/aaron12/2010/04/14/test-smtp-post/#respond )

I just get a blank page. Does anyone know what I could look at to see what is going wrong?

Yes, your error logs.

blank page = errors. These are logged by your server in a file somewhere.

Ad Andrea said, blank pages means server errors. Somewhere it is throwing a php fatal error. In your CPanel check "Error logs". Just to make sure, just visit one of those links that gives error, and then check the "Error logs".

Thanks, just trying to work out where to access the error logs from Streamline.net account.

Ok, my error log says:

[Thu Apr 15 18:04:59 2010] [alert] [client 86.186.48.102] /home/fhlinux130/o/oliverquinlan.co.uk/user/htdocs/rhs/blogs/.htaccess: RewriteBase: argument is not a valid URL

Any ideas?

My .htaccess file reads:

RewriteEngine On
RewriteBase /rhs/blogs/

#uploaded files
RewriteRule ^(.*/)?files/$ index.php [L]
RewriteCond %{REQUEST_URI} !.*wp-content/plugins.*
RewriteRule ^(.*/)?files/(.*) wp-content/blogs.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteCond %{REQUEST_URI} ^.*/wp-admin$
RewriteRule ^(.+)$ $1/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule . - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-.*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

<IfModule mod_security.c>
<Files async-upload.php>
SecFilterEngine Off
SecFilterScanPOST Off
</Files>
</IfModule>