[Plugin: W3 Total Cache] Unable to add 'define('WP_CACHE', true);' to Config.php

I’m receiving a message that Page Caching is unavailable until define(‘WP_CACHE’, true); is placed in the wp-config.php file.

However when I do that, both the site and the admin area go down, and I’m left with just this message:

Parse error: syntax error, unexpected T_STRING in /home2/mdleepho/public_html/tallandsmallphotography/wp-config.php on line 5

Not quite sure what’s going on here…