First, check the "index.php" file in your main directory. In that file there is a path to the blog header which loads the theme, etc. Check the path for accuracy because without a correct path, all you get is text and no theme.
Second, If you did what I did when setting up Wordpress, that is to get everything setup and then decide to move things around a bit, then most likely you forgot to change the settings to match your changes. In particular, the database may not have updated so that it is still trying to draw on a file that is no longer there, such as a domain URL, theme, etc. You can check the database to make sure the URL is correct by visiting: Wordpress: Changing the Site URL
. Page down to the section entitled: Changing the URL directly in the database. There are two places to check within the database. Do be careful, but see of that works for you.
Lastly, sometimes you might need to uninstall a theme, widget or plugin and then reinstall it to get it to render again properly, especially if you happened to update Wordpress to a newer version just before the problem occurred.