Are you sure that the correct virtualhost is used? Have you put the statement "RewriteEngine on" in front of these rules?

do you get that message from the httpd or from AEM?And is the $Server_hostname really identical to the one you used in the request? You can increase the loglevel of the dispatcher to DEBUG to see if the dispatcher is consulted for this request or if the problem is the httpd itself. And in that case the dispatcher also logs enough information to see what AEM is doing; just addDispatcherLogLevel 3into the section and restart the httpd.