object-cache.php warning

I am getting this message when trying to access my website. It is not happening every time, but the frequency is increasing and seems to be on desktop only. Any ideas?

Warning: Class __PHP_Incomplete_Class has no unserializer in /home/content/p3pnexwpnas01_data03/60/2196960/html/wp-content/object-cache.php on line 520

Warning: Cannot modify header information – headers already sent by (output started at /home/content/p3pnexwpnas01_data03/60/2196960/html/wp-content/object-cache.php:520) in /home/content/p3pnexwpnas01_data03/60/2196960/html/wp-includes/pluggable.php on line 1171

My website is:
http://www.iamahomemaker.com