I am having the same “empty cart” problem, which occurs in Firefox, Chrome, and IE. I do not have a caching plugin activated, and just upgraded to Cart66 1.4.2. When that didn’t work I disabled the database sessions. Still no help. It appears Cart66 is not creating a WP_Cart66_sessions file. I’ve tried deactivating and reactivating the plugin several times, and have done the same for the rest of my plugins without result. If anyone has another suggestion I would love to hear it.