Markers not opening. Please help!!

I believe I'm having a similar problem as Claire. Is there a maximum number of markers recommended or allowed in a course? I'm wondering if I've perhaps overwhelmed the course by using too many? The markers work fine for me during preview mode, and they also work fine for me when I open the published file, however my clients are experiencing an issue where the markers will work fine for a while, and then (for no apparent reason) the markers stop working. They've tried opening the file in several different browsers. They've also experienced this issue on several different laptops. Thoughts? I'm getting ready to delete the markers and create triggers to new layers (which I don't want to have to do), but it's the only thing I can think of at this point to solve for this issue.  

(FYI - I've got 65 markers in the course.)