Won't update

I am trying to update my “about” page on my blog which I published two years ago. After making changes and hitting update I get this message: Warning: Incorrect cache engine in /home/content/96/7104096/html/wp-content/plugins/w3-total-cache/lib/W3/Cache.php on line 76 Warning: Cannot modify header information – headers already sent by (output started at /home/content/96/7104096/html/wp-content/plugins/w3-total-cache/lib/W3/Cache.php:76) in /home/content/96/7104096/html/wp-includes/pluggable.php on line 876. How can I make the needed changes?