I've gotten a similar error from 2 different plugins and haven't been able to resolve them. I'm wondering if it might be a theme error.
I used WP Ultra Simple Paypal Shopping Cart. When I add an item and them try to delete it from the cart I get - Warning: Invalid argument supplied for foreach() in /home/content/p3nexnas05_data03/59/2166859/html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wp_ultra_simple_shopping_cart.php on line 152
I just updated JetPack plugin and got - Warning: Invalid argument supplied for foreach() in /home/content/p3nexnas05_data01/75/2167375/html/wp-content/plugins/jetpack/class.jetpack.php on line 4470
Is it possible the them is the issue here?