Error 500 with Prosites/Pay to Blog

I sent myself an email to see if the entire blog creation process would work.

I get an activation email, but when I click it, it gives me an error 500.

this is my activation email

To activate your blog, please click the following link:

After you activate, you will receive *another email* with your login.

After you activate, you can visit your site here:

This is what my htaccess file says

# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]

# END WordPress