Site will not upgrade from 3.0.1 to 3.3.1

A site I am managing is currently running version 3.0.1. I have tried updating the site to 3.3.1 via the auto update, but it crashes the site. I have also tried manually, and this crashed it as well. I have another guy who is helping me and we have not been able to resolve the issue. We believe it has something to do with either the plugins or the theme that is currently applied. I have listed the plugins below that we are currently using. Does anyone have any suggestions as to what may be the cause? Thanks for helping!

[Plugin list moderated]