update magento static block programmatically through upgrade scripts

data-install-0.0.0.1.php

<?php
/* @var $installer Mage_Core_Model_Resource_Setup */
$installer = $this;

$installer->startSetup();

$connection = $installer->getConnection();

$identifier = 'id-goes-here';
$title = 'Title Goes Here';

$contentCmsBlock = <<<EOT
<div id="$identifier">
     <p>Put your content here.</p>
</div>
EOT;

$cmsBlock = Mage::getModel('cms/block')->load($identifier);

if ($cmsBlock->isObjectNew()) {
    $cmsBlock->setTitle($title)
        ->setContent($contentCmsBlock)
        ->setIdentifier($identifier)
        ->setStores(0)
        ->setIsActive(true);
} else {
    $cmsBlock->setTitle($title)
        ->setContent($contentCmsBlock)
        ->setStores(0)
        ->setIsActive(true);
}

$cmsBlock->save();

$installer->endSetup();

setStores() must get an array as a parameter, or use setStoreId() to give only a unique Id.