Posts in category archive losing formatting

I am a beginning user of WP. My problem is that when a post is archived in a category, the image doesn’t show up and the post has lost its formatting. If you click on the title of the post (in the archive), it shows OK. Here is my blog: http://mrmarketrules.com
I know the problem might be in the theme I’m using, because I have another blog, with a different theme, and don’t have the same trouble. Thanks.