W3 Cache Plugin trouble

Since I updated to 3.4, my W3 Cache plugin is causing my slider and contact form not to load. When I active it the loading haults. As soon as I deactive the plugin the site loads fine. Not sure if it is W3 Cache or a conflict with another plugin. My site is running ok without W3 Cache but I want all the benefits of W3.

I am a beginner in Word Press and need to know best practices when updating the software. Should I deactive all pluggins before I update Word Press? Is there a certain order to updating plugins?

I know there is a new update to Word Press, and I want to attempt the upgrade but wanted to do it right the first time.

Any help would be appreciated.