This error has to do with the “RewriteRule” directive into .htaccess. Maybe your Apache’s configuration has anything on not accepting that.
You can configure WordPress on using different ways for passing posts information, though. One of them (and this one maybe is set for you) uses this Apache directive for redirecting the URI throw index.php, another one is by passing variables throw GET (you should try this instead), Go to:
ADMIN/OPTIONS/Permalink (choose the default).
