File not found log error .. What is triggering it? How to fix it?

Question

I have this log error:

[Wed Jul 21 10:40:17 2010] [error] [client 195.229.242.57] File does not exist: /var/www/vhosts/kranichs.com/httpdocs/products, referer: http://www.kranichs.com/products/Kranichs/ring-2194

I am assuming this has something to do with the page's URL is really something like

kranichs.com/product_page.php?id=2194

But is made pretty using mod_rewrite and maybe something on that page is requesting something with a relative URL and so its coming up as file not found?

But on the page I have this which I thought resolved that:

<base href="http://www.kranichs.com/" />

So I am not exactly sure what the error means or how to fix it?