Service/Amazon/S3.php not being found

Here's the sample code from the sample: <?php echo 1; require_once('Service/Amazon/S3.php'); echo 2; // Replace with your own credentials $accessKeyId = 'xxxxxxx'; $secretAccessKey = xxxxxxxxxxxx; $s3 = Services_Amazon_S3::getAccount($accessKeyId, $secretAccessKey); foreach ($s3->getBuckets() as $bucket) {  print "<li>" . htmlspecialchars($bucket->name) . "</li>"; } ?> Here's what I have on the server: Archive_Tar        1.3.2   stable Auth               1.6.1   stable Console_Getopt     1.2.3   stable Crypt_HMAC         1.0.1   stable DB                 1.7.13  stable HTML_Common        1.2.4   stable HTML_QuickForm     3.2.10  stable HTTP_Request       1.4.3   stable HTTP_Upload        0.9.1   stable MDB2               2.4.1   stable MDB2_Driver_mysql  1.4.1   stable Net_Socket         1.0.9   stable Net_URL            1.0.15  stable PEAR               1.7.2   stable Pager              2.4.7   stable Services_Amazon_S3 0.1.0   alpha Structures_Graph   1.0.2   stable XML_RPC            1.5.1   stable After install, I restarted the web server. When I run it, it stops at "1" (see echo in code above so it is failing at: require_once('Service/Amazon/S3.php'); so something is wrong. Any ideas?