It is acting like the mod rewrite isn't running at all. It thinks you are referencing a folder and then redirects to 403 page. I think it is a server configuration issue of some sort. The problem isn't on the newsarticle.php page since you can access the page with a modified link without problems.
The .htaccess file appears to be ignored.
I tried stripping the .htaccess file so that it only had the one rewrite rule and the issue still persists.
I even tried just doing a very simple rewrite rule and it doesn't appear to work. so it has to be a configuration issue of some sort.