Thanks for the screenshots and the additional information. From your screenshots, it looks like the stylesheets are not loading. The stylesheets are what give the blog its design.
However, the Suburbia demo site and your blog both look just fine to me. The problem is not occurring on my end.
So that we can troubleshoot the problem, can you check a few things for me?
1. First, can you load http://twentytwelvedemo.wordpress.com and tell me if the same problem occurs? I'm trying to establish if this problem occurs with other themes, too.
2. Can you clear your browser's cache and cookies and then reload your site to see if that fixes it?
3. Do you have access to another computer? If so, can you view your blog on that computer to see if the problem still occurs?
4. Are you viewing your site on a school or similar network that might have blocks or restrictions in place? They might be preventing our stylehsheets from loading. Try viewing your site on a computer connected to a different network. For example, a public library, or maybe a friend's house. Does the problem still occur?
Let me know when you've tried these things, and if the problem still occurs.