If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule
Invalid command ‘ProxyRequests’, perhaps misspelled or defined by a module not included in the server configuration
Invalid command ‘RequestHeader’, perhaps misspelled or defined by a module not included in the server configuration
.htaccess: Invalid command ‘RewriteEngine’, perhaps misspelled or defined by a module not included in the server configuration
