The ‘default’ theme that you are using is built using a php file that converts to CSS at run time. Looking at your site as a guest I can see that it has not been built and is therefore missing most of the rules. However  – why it should successfully build when logged in and not otherwise is a mystery and is going to be environmental in some way.

One thing you could try would be to turn on the compression and CSS cache (options > global) and them IMMEDIATELY run your forum. If that looks OK see if it holds for non-logged in users. But there is an underlying reasons why things are happening and it would be much better to resolve those. Something is stopping the php being executed…

You also have a javascript issue with your site which WILL effect the forum and possibly other plugins as well. Your WP theme is riding roughshod over the WP API and loading a second, older and non-standard copy of the jQuery library and this is triggering errors. This is explained here:

http://codex.simple-press.com/codex/faq/troubleshooting/what-is-this-jquery-conflict/

Thanks for the quick response.  But before I read your response I changed the CSS/JS Combined Caching to “Enable comibining and caching of forum CSS files” and it seemed to fix it.  I will look into the other errors you are talking about.  

How are you able to tell that I have a javascript issue? I want to be able to explain it to the person i bought the theme from.

By using the script console that most browsers are now equipped with although I use Firebug – Firefox extension for this as it is probably the best out there. But just loking at your html source to see what is getting loaded is enough. If you see multiple instances and versions of any script then there is a problem waiting to happen.

These things are usually pretty easy to fix up.

Ok.  Im familiar with firebug.  I will take a look at it.

Good news.