Yes, it looks like a template issue with the popup month window. Look for this code in your template.css file:
.art-post ul li, .art-post ol ul li {
background-image: url("../images/postbullets.png");
background-repeat: no-repeat;
overflow-x: auto;
overflow-y: auto;
padding-left: 11px;
}
If you remove the overflow-x and overflow-y lines, it works. I'm not sure how that will affect other parts of the site.
Thanks for the suggestion. There is an image available in the popup window when hovering over an event. If you have HTML enabled for the event descriptions. The first image (if any) of the event description will be diplayed in the popup window.