Just want to drop a note, W3 Total Cache caused all kinds of problems on my own e-commerce site a little while back and even after I deleted the plugin, I still had same issues. After digging deep, I realized W3 Total Cache left lingering files that affected the whole site. It is not until I manually deleted these lingering files is where I got my site back up.
I am sure it is not the fault of W3 Total Cache but just my lack of understanding on how to configure it to work with e-commerce type sites.
But just want to state that if you want to check...