I removed W3TC a while ago, but seems some bits and pieces are still lying around, e.g. I can see
/wp-content/w3-total-cache-config-preview.php
/wp-content/w3-total-cache-config.php
/wp-content/w3tc-config/index.html
/wp-content/w3tc-config/master.php
/wp-content/w3tc-config/master-admin.php
This could very possibly be the reason that after updating to 3.5.2 I can't access my site or backend http://wordpress.org/support/topic/upgrading-to-352-failed-and-now-fatal-error
Please advise as to how I can clean up the W3TC residue.