I figured it out by piecing together a few solutions from other uses of this theme. Basically, a quick three-step solution (which assumes you have kept basic style names intact and not made earthshaking modifications to the CSS configuration).
1). These lines in your main CSS file:
This ensures that the accordion content never displays on pageload.
2). The problem now is to "overcome" the style attribute in the mootools script. The script as written fails to do this. Here's a modified version to compensate:
[Code moderated as per the Forum Rules. Please use the pastebin]
3. This creates a problem with the .contentheader style as the theme uses it in archive.php and search.php (because the "Search Results" header is in the same style as the post name, and thus tries to hide its subordinate content per the rules of the script). To fix this I had to duplicate the css entries for .contentheader as .contentheader2 and adjust the php accordingly.
I hope this helps! I haven't had any overdue slowness with the theme. When I was troubleshooting the pageload question, I routinely disabled all plugins and that never seemed to adjust load times one way or another. I use WP Super Cache without any strong difference in load time (for a site with admittedly very little data content to load in the first place).