URLrewrite为啥会错呢

URL rewrite为什么会错呢？

RewriteEngine On
RewriteBase /forum
RewriteRule ^((Index|List|Content|admin|Vote|Message|Favor).*)$ index.php/$1


提示
Not Found

The requested URL /forum/List-index-f-2.shtml was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

但是我写
RewriteRule 1.php 2.php 又是对的，令人费解

------解决方案--------------------
请确认RewriteBase 路径是否正确。