I have been setting up the Courspress Pro plugin on my site, and noticed that the signup form was not working. After digging around, I discovered that invalid HTML in the shortcode which creates the form was the cause of the incompatibility with my theme. I have it fixed now, but I would have to go in and change it every time the plugin is updated.
The issue can be found on line 4076 of coursepress/includes/classes/class.shortcodes.php:
<div class="clearfix" style="clear: both;" />
<div class="clearfix" style="clear: both;"></div>
I haven't looked through to find if this is used anywhere else, but I think it would be appropriate if you changed it anywhere that you know of.