WordPress MU

Hi,
Installation went fine. When I try to log in to admin i get this message from the browser. this occurs when install choosing sub-directories for blogs but not if I choose sub-domains.
Can anyone please tell me why this happens?

The page isn't redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

* This problem can sometimes be caused by disabling or refusing to accept
cookies.

You did enable mod_rewrite didn't you?

Is there anything in the apache error log?

Also, if you used www. in your url, try reinstalling without the www.

thanks for the replies.
yes; i dont know; and i didnt use www.

my htaccess looks like this:

could something in here like adding slashes cause this?
thanks again

Options +FollowSymLinks
RewriteEngine On
RewriteBase /

#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>

Check your apache error logs, if you've got a looping rewrite then you should see something in there about that.