WakeUpWorld on "[Plugin: W3 Total Cache] 500 Internal Error on Admin - Public View of Site Ok"

Thanks for your reply mykkal.

I found the most basic version (as per below) and uploaded it via ftp, but still can not access wp-admin

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

I also added in "memory_limit = 64M" into the php.ini file