I've come across a few particular courses where it takes forever to load just that course.
One way to fix it is to delete the course and have the user start from scratch, but obviously this isn't a great option.
I deleted all blocks except administration, and this did not clear up the loading time.
I also ensured there were no large images in any of the topics via either a topic summary or a label.
Still the site takes over a few minutes to load. What else could be causing this? All other courses load rather quickly on the moodle server.