WordPress MU

When using the .htaccess file that comes with wpmu 2.6.5 I got a 500 error, logs said: "RewriteBase takes one argument, the base URL of the per- directory context"

The first few lines were:
_________________________________________
php_flag register_globals 0
php_flag display_errors 0

RewriteEngine On
RewriteBase BASE/

#uploaded files
RewriteRule ^(.*/)?files/$ index.php [L]
...etc
_________________________________________

If you don't use this htaccess file, then links to uploaded pics & otherfiles don't work.
I deleted BASE as follows now everything works fine:
____________________________________________
php_flag register_globals 0
php_flag display_errors 0

RewriteEngine On
RewriteBase /

#uploaded files
RewriteRule ^(.*/)?files/$ index.php [L]
...etc
_____________________________________________
this has taken me about3 days to work out, so I hope it helps some of you out there!

Actually, the line

RewriteBase BASE/

exists in htaccess.dist and when you install WPMU it becomes

RewriteBase /

I've found that when folks have this problem, they haven't set the directory mu sits in to be writable by the server as noted in the directions or they have the cpanel problem:

http://mu.wordpress.org/forums/topic.php?id=99