These two options are available under lifetype:
base_url
Base URL where this blog is installed
subdomains_base_url
When subdomains are enabled, this base URL is used instead of base_url. Use {blogname} to get the blog name, {username} to get the name of the user owner of the blog and {blogdomain} to allow the user to specify any subdomain in order to generate a link to a blog. (e.g.. http://{blogname}.yourdomain.com)
Please include them also in MU they will finally resolve all thread related to htaccess problem! :)