Google Analytics doesn't track 404 correctly

I followed Google recommendations but doesn't work to me

[Chuck Norris]

I followed google recommendations to track 404 errors ( [analytics.blogspot.com...] )

It show the visitors but it doesn't show the error pages. I only get this:

/404.html
1.page=/404.html

This is the code I'm using and it seems right:

<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-9603-1";
urchinTracker("/404.html?page=" + _udl.pathname + _udl.search);
</script>

Anybody knows how to make it work?