One major problem we had was in task six. Users did not completely understand the difference between an event, an article, and a discussion. This had somewhat to do with the way the paper prototype implemented the "create new post" window. We didn't have any affordances to specify that for an event required a location, a date, and a time, nor that an article required a link. In addition, we feel they did not understand how they could interact with the different type of posts (for example, clicking an article in the main window leads to the article, but clicking a discussion in the main window leads to a "comments section" without any article).
In this iteration we used "tags" instead of "topics." This confused the user, as they did not understand that "tag" meant the same thing as "topic." In particular, one user thought tag meant the link of the article.
One user had a serious problem with task four and got stuck for a while. Our "add topic" icon was a simple plus sign, and he did not understand what it stood for.
One user did not understand

found the comments section confusing. In particular, she couldn't see who posted the topic, nor found it easy to view her own comments.
One user had trouble finding the "New Post" link. Considering it was blown up and should have been very visible, this posed a problem.

Second Prototype

Changes

We didn't want to drastically alter our design since the users did not have too much trouble viewing