Expression engine page sometimes not found with www, found with non-www - .htaccess

Question

I'm having a strange problem with an ExpressionEngine 1.6 site. I have added a page, and some people have had difficulty accessing the page with www. in front of the URL. Without the www, there seem to be no problems. It also seems to depend on which browser I am using - if I use Chrome, I cannot see the page with www in the URL, but I can if there is no www. Other browsers work whatever. I've tried clearing cache in Chrome to no avail.
What on earth could the problem be?
Here's the code in .htaccess, in case it's something to do with that.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond $1 !\.(gif|jpe?g|png)$ [NC]
RewriteRule ^(.*)$ /index.php/$1 [QSA,L]
RewriteCond %{QUERY_STRING} ^utm_medium
RewriteCond %{REQUEST_URI} ^/$ [NC]
RewriteRule (.*) /index.php?/pages/index/&%{QUERY_STRING} [L]
</IfModule>

Answer 1

It's not ideal to have a site that's accessible on both the www and no www as this will mean your Google listing gets diluted due to duplicate content. By eliminating the www you will also resolve your issue:
# Remove the www from the URL
# ------------------------------
RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
Should go after the line "RewriteBase /" and before your main rewriting.
The alternative is to add the www:
# Add the www to the URL (use instead of www removal)
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteCond %{HTTP_HOST} !^localhost [NC]
RewriteRule (.*) http://www.%{HTTP_HOST}/$1 [R=301,L]
That said, to try and specifically solve the issue, I'm assuming that other pages are fine and it's just this page in particular? Also can the page be accessed by including the index.php/ in the path?
This rewrite seems a bit strange:
RewriteCond %{QUERY_STRING} ^utm_medium
RewriteCond %{REQUEST_URI} ^/$ [NC]
RewriteRule (.*) /index.php?/pages/index/&%{QUERY_STRING} [L]
If this line is the culprit and relevant to the page causing issue, try changing the last line:
RewriteRule ^(.*)$ /index.php?/pages/index/&%{QUERY_STRING} [L]
or
RewriteRule (.*?)index.php?/pages/index/&%{QUERY_STRING} [L]