Thinking more...

I met this warning message when I restart Apache httpd(My machine run CentOS 4.5):

Starting httpd: [Tue Oct 30 07:39:41 2007] [crit] The unix daemon module not initialized yet. Please make sure that your mod_mono module is loaded after the User/Group directives have been parsed. Not initializing the dashboard.

Then I Google it, I found that someone had asked:[Mono-list] Errors after update....:(
The solution is very easy. Just open your httpd.conf, and make sure

User apache
Group apache

is placed behind

Include conf.d/*.conf

, then restart Apache httpd.