Formatting Error

I haven’t seen that happen. Do you have a link to a site that it’s happening on?

Looks like it’s a conflict with some pretty generic rules in your theme that apply to .entry-content. Adding these rules to your theme’s CSS file will help:

.widget_twitter .entry-content {
	background: none;
	padding: 0;
}
.widget_twitter ul li {
	padding-bottom: 1em;
}