Rewrite base

I am trying to turn on the network on my testing server prior to doing it for my production server. At the network install, I was advised to add specific code to wp-config and .htaccess. Having done that, I would be all set as soon as I logged in again. I cut and paste them in, and promptly got a 500 internal error when I tried to log in again. I looked at the localhost error log, and saw this:

[Fri Apr 29 21:19:39 2011] [alert] [client 127.0.0.1] C:/Apache2/htdocs/Semantic Law/.htaccess: RewriteBase takes one argument, the base URL of the per-directory context, referer: http://localhost/Semantic%20Law/wp-admin/network.php

Note, I took the .htaccess code as it was given to me. But looking at this I thought maybe it was trying to tell me that the base should be SemanticLaw.net/wp-admin, but that seems to have made no difference with or without the trailing slash. So I don’t know what’s wrong or how to fix it.

Here is the code I was given for .htaccess at the network install:

RewriteEngine On
RewriteBase /Semantic Law/
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

I also ran a search for the language of the error code but came up empty, which I thought was curious since I can’t be the first or only one with this issue.
As always, your helpful insights greatly appreciated.