Since Google doesn't index SSL pages, here's a way to get PHP to ignore the code when in SSL mode, and you won't get the nonsecure items popup:
CODE
<?php
if ( $request_type != 'SSL' ) {
?>
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-xxxxxxx-x";
urchinTracker();
</script>
<?php
}
?>
if ( $request_type != 'SSL' ) {
?>
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-xxxxxxx-x";
urchinTracker();
</script>
<?php
}
?>
Wrap the PHP code around your google-analytics script as shown above.

