Temporary 'fix' for static block caching issue in Magento 1.9.2 (app/code/local/Mage/Cms/Block/Block.php)

Block.php

<?php
/**
 * ************************************************************************************
 * ***************ATTENTION*************************************************
 * This is the temporary fix for the Magento 1.9.2 bug
 * See http://magento.stackexchange.com/q/73685/3112?stw=2
 * The only change from app/code/core/Mage/Cms/Block/Block.php
 * is that the getCacheKeyInfo() function below is added.
 * Thanks to andrewkett for the solution!
 * ****************************************************************
 * 
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magento.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magento.com for more information.
 *
 * @category    Mage
 * @package     Mage_Cms
 * @copyright  Copyright (c) 2006-2015 X.commerce, Inc. (http://www.magento.com)
 * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */


/**
 * Cms block content block
 *
 * @category   Mage
 * @package    Mage_Cms
 * @author     Magento Core Team <core@magentocommerce.com>
 */
class Mage_Cms_Block_Block extends Mage_Core_Block_Abstract
{

    /**
     * Initialize cache
     *
     * @return null
     */
    protected function _construct()
    {
        /*
        * setting cache to save the cms block
        */
        $this->setCacheTags(array(Mage_Cms_Model_Block::CACHE_TAG));
        $this->setCacheLifetime(false);
    }

    /**
     * Prepare Content HTML
     *
     * @return string
     */
    protected function _toHtml()
    {
        $blockId = $this->getBlockId();
        $html = '';
        if ($blockId) {
            $block = Mage::getModel('cms/block')
                ->setStoreId(Mage::app()->getStore()->getId())
                ->load($blockId);
            if ($block->getIsActive()) {
                /* @var $helper Mage_Cms_Helper_Data */
                $helper = Mage::helper('cms');
                $processor = $helper->getBlockTemplateProcessor();
                $html = $processor->filter($block->getContent());
                $this->addModelTags($block);
            }
        }
        return $html;
    }

    /**
     * 
     * If this block has a block id, use that as the cache key.
     *
     * @return array
     */
    public function getCacheKeyInfo()
    {
        if ($this->getBlockId()) {
            return array(
                Mage_Cms_Model_Block::CACHE_TAG,
                Mage::app()->getStore()->getId(),
                $this->getBlockId(),
                (int) Mage::app()->getStore()->isCurrentlySecure()
            );
        } else {
            return parent::getCacheKeyInfo();
        }
    }
}

To implement 'this' fix simply add this file at YOUR_MAGENTO_DIRECTORY/app/code/local/Mage/Cms/Block/Block.php
You'll be able to use block cache again until the fix is released by Magento. You should remove this file before you update Magento.

Thanks to andrewkett for the solution.