[Plugin: WP Super Cache] Installed, but doesn’t appear to be working (??)

I installed wp-super-cache via the “Add new” plugins page, and it seemed to go fine (no errors). However, it doesn’t seem to be working. When I log out and view pages, I always see something like this at the bottom if I do a View|Source:

<!– Dynamic page generated in 0.244 seconds. –>
<!– Live page served on 2010-04-25 16:14:52 –>

Control panel Settings are:
[ON] WP Cache and Super Cache enabled
[X] Don’t cache pages for logged in users.
[X] Cache rebuild.

(I never installed “WP Cache”, co I don’t know why it even mentions it. (??)

Cache Contents are as follows:
WP-Cache (0KB)
* 0 Cached Pages
* 0 Expired Pages

WP-Super-Cache (0KB)
* 0 Cached Pages
* 0 Expired Pages

In the wp-super-cache control panel it mentioned that I had to add some lines to the .htaccess for WPMU. I did so, and it also indicated that lines needed to be added to the .htaccess file in the /wp-content/cache/.htaccess file too, but they were already there. (??)

This is the current .htaccess file, after adding the lines:

RewriteEngine On
RewriteBase /blogs/

# BEGIN WPSuperCache
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blogs/
AddDefaultCharset UTF-8
RewriteCond %{REQUEST_URI} !^.*[^/]$
RewriteCond %{REQUEST_URI} !^.*//.*$
RewriteCond %{REQUEST_METHOD} !POST
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{HTTP:Cookie} !^.*(comment_author_|wordpress|wp-postpass_).*$
RewriteCond %{HTTP_USER_AGENT} !^.*(2.0\ MMP|240x320|400X240|AvantGo|BlackBerry|Blazer|Cellphone|Danger|DoCoMo|Elaine/3.0|EudoraWeb|Googlebot-Mobile|hiptop|IEMobile|KYOCERA/WX310K|LG/U990|MIDP-2.|MMEF20|MOT-V|NetFront|Newt|Nintendo\ Wii|Nitro|Nokia|Opera\ Mini|Palm|PlayStation\ Portable|portalmmm|Proxinet|ProxiNet|SHARP-TQ-GX10|SHG-i900|Small|SonyEricsson|Symbian\ OS|SymbianOS|TS21i-10|UP.Browser|UP.Link|webOS|Windows\ CE|WinWAP|YahooSeeker/M1A1-R2D2|iPhone|iPod|Android|BlackBerry9530|LG-TU915\ Obigo|LGE\ VX|webOS|Nokia5800).*
RewriteCond %{HTTP:Accept-Encoding} gzip
RewriteCond %{DOCUMENT_ROOT}/blogs/wp-content/cache/supercache/%{HTTP_HOST}/blogs/$1/index.html.gz -f
RewriteRule ^(.*) /blogs/wp-content/cache/supercache/%{HTTP_HOST}/blogs/$1/index.html.gz [L]

RewriteCond %{REQUEST_URI} !^.*[^/]$
RewriteCond %{REQUEST_URI} !^.*//.*$
RewriteCond %{REQUEST_METHOD} !POST
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{HTTP:Cookie} !^.*(comment_author_|wordpress|wp-postpass_).*$
RewriteCond %{HTTP_USER_AGENT} !^.*(2.0\ MMP|240x320|400X240|AvantGo|BlackBerry|Blazer|Cellphone|Danger|DoCoMo|Elaine/3.0|EudoraWeb|Googlebot-Mobile|hiptop|IEMobile|KYOCERA/WX310K|LG/U990|MIDP-2.|MMEF20|MOT-V|NetFront|Newt|Nintendo\ Wii|Nitro|Nokia|Opera\ Mini|Palm|PlayStation\ Portable|portalmmm|Proxinet|ProxiNet|SHARP-TQ-GX10|SHG-i900|Small|SonyEricsson|Symbian\ OS|SymbianOS|TS21i-10|UP.Browser|UP.Link|webOS|Windows\ CE|WinWAP|YahooSeeker/M1A1-R2D2|iPhone|iPod|Android|BlackBerry9530|LG-TU915\ Obigo|LGE\ VX|webOS|Nokia5800).*
RewriteCond %{DOCUMENT_ROOT}/blogs/wp-content/cache/supercache/%{HTTP_HOST}/blogs/$1/index.html -f
RewriteRule ^(.*) /blogs/wp-content/cache/supercache/%{HTTP_HOST}/blogs/$1/index.html [L]
</IfModule>
# END WPSuperCache

#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>

In any case, if I log out I don’t see any cached files being served, and there are no files at all in the supercache directory. I went to each blog and manually activated the plugin, but no joy. How do I enable caching?? What am I doing wrong??