I logged into the server and took a peek; your permissions are seriously messed up. They are set to 777 on all files and folders which, with poorly coded scripts (and some well-coded ones) is a security risk - the server automatically throws a "403 Forbidden" in this instance.
You'll need to do a permissions change; folders should be at 755 and no higher, files at 644. This should resolve the 403 error, along with adding some extra security to the site. With 777 permissions, a wider range of scripting exploits/hacks become possible - we get enough of these on 755/644 as it is, so the server is set up to help protect itself by denying 777 as a valid permission set for now.