Shoutbox 1.4? 1.3 I think is the latest, I can't tell since you've made modifications.
I am using the same version number right now and page works just fine. This was a security WP update, so perhaps something else was accidently changed in one of the template files most likely. Your html is completely off with your footer and part of the main content area are in the wrong place.. You said this just happened after the update ?
One of your plugins i think is going nuts, because if you look further on in chrome developer tools, you will see that the bottom half of the website is inside a 60px width table . I checked the source code of the theme and that table doesn't exist. Please take a look at your plugins, since you have the same files being loaded multiple times even in the image you posted above. There are enclosed div/span tags all over.
My suggestion is to completely delete all folders except wp-content and the .htaccess and wp-config.php and using ftp upload a fresh copy of Wordpress. Also Please compare the theme you customized to the original on a character by character basis using winmerge.org and you are sure to find the missing div from modified template files. First thing though, is remove the plugins please.