WP Super Cache killed my site

If it’s really a wp-super-cache problem:

Make a fresh backup of your installation (I’m not kidding) and delete the following

wp-content/advanced-cache.php (this should be a symlink)
wp-content/wp-cache-config.php
wp-content/plugins/wp-super-cache (the plugin directory)
wp-content/cache/wp-cache*
wp-content/cache/supercache (also a directory)

Now in your wp-config.php (MAKE ANOTHER BACKUP) edit the file and remove the line that says this:

define('WP_CACHE', true); //Added by WP-Cache Manager

Now make a backup of your .htaccess file. Remove the lines that looks something like this:

# BEGIN WPSuperCache
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /wordpress/
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:Accept-Encoding} gzip
RewriteCond %{DOCUMENT_ROOT}/blog/wp-content/cache/supercache/%{HTTP_HOST}/blog/$1/index.html.gz -f
RewriteRule ^(.*) /blog/wp-content/cache/supercache/%{HTTP_HOST}/blog/$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 %{DOCUMENT_ROOT}/blog/wp-content/cache/supercache/%{HTTP_HOST}/blog/$1/index.html -f
RewriteRule ^(.*) /blog/wp-content/cache/supercache/%{HTTP_HOST}/blog/$1/index.html [L]
</IfModule>

# END WPSuperCache

After that’s done try accessing your blog. If it makes it worse, restore the full backup I said to make in the beginning.

As Donncha said, you also need to look at your error_log file that your web server creates. If you are on a hosted environment, ask your provider for that file.

Don’t use it if you don’t want to, but it’s an awesome plugin when you need it.

If you can, try to find out what the error was from the log.

Either way restoring your backup should set you right.