I have a non-superuser account that needs the ability to add a new page. 

This user can already edit pages that already exist, but when I go to the Personal Bar > Pages I get a blank page with an error at the top: "There was an error retrieving your content. Please check your internet connection".

No. The users do not have the Administrator permission. I don't want them to be able to be able to do everything an Administrator can do. For example, I'd like the workflow to be locked in so they can't publish pages.

I'd like a role that has very little control. They'd have the ability to exist existing pages as drafts, create new pages as drafts and upload files in the assets manager. They're would also be a content manager role which could do all of that, but also could publish the pages.

EVOQ has both a content manager and content editor role, but the content editor can change the workflow from Content Approval to Direct Publish, which defeats the purpose of the role even existing.