Certain pages are broken

Hi,

At this time, my header contains four sections: About, Contact, Archives, and Clips.

Somehow, I got About and Contacts to work, but when I click on either Archives or Clips, I’m brought to a page-not-found error from my host (as opposed to WordPress).

I’ve researched this issue, and it seems to be common, but I can’t figure how to implement the solution. From what I can tell, I need to change my permalinks and my .htaccess file, but, to put it simply, I’m lost.

1. Via Options/Permalinks, I’m using the following syntax for permalinks:

/%year%/%monthnum%/%day%/%postname%/

2. Here’s the content of my .htaccess file, which is in the same directory as my index.php file:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

3. And here’s what I think is the relevant section of my Header file (at least I think it’s relevant because I’ve been tinkering with it):

<ul id="nav">

		<li><a <?php if (is_page('about')) echo('class="current" '); ?>href="<?php bloginfo('url'); ?>/about/">About</a></li>
		<li><a <?php if (is_page('contact')) echo('class="current" '); ?>href="<?php bloginfo('url'); ?>/contact/">Contact</a></li>
		<li><a <?php if (is_archive() || is_page('archives')) echo('class="current" '); ?>href="<?php bloginfo('url'); ?>/archives/">Archives</a></li>
		<li><a <?php if (is_page('clips')) echo('class="current" '); ?>href="<?php bloginfo('url'); ?>/clips/">Clips</a></li>
		<li class="rss"><a href="<?php bloginfo('rss2_url'); ?>"></a></li>
	</ul>

4. Finally, I’ll note that in my Theme Editor, I have two Archives files.

Can anyone help me sort out this mess? Many thanks!