I’ve just had this issue too, and like others, this fixes it nicely. The problem is that in the jQuery used in the preloadImages function selects ALL images in the page, not just the ones inside the event calendar.
This fix shouldn’t make anything else break, as all it does is change the image URLs to loading.gif. It just means that the images will appear when they appear, rather than having a progress bar, I prefer it without the progress bar anyway.