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.
