I encourted a problem that I couldn’t see the dialog for my password protected pages. The problem was caused by Wordpress default .htaccess file which redirect 401 page to 404 page. The more detail can be found here (http://www.andrewrollins.com/2008/01/22/wordpress-and-htaccess-password-protected-directories/)
I’ve tried three methods the article said and only found the last one is OK. I created a 401 page and put this line into .htaccess and every went well.
ErrorDocument 401 /401.shtml
I didn’t know the reason for the failure of another two failed because my new hosting server is LiteSpee which may not fully compatible with Apache.