Using 1.7.8 today I ran across a bug in Zend_Db_Profiler_Firebug. If you have filtered, for example, select queries from profiling an exception is thrown on line 131 when the profiler cannot find the $queryId, which was unset in Zend_Db_Profiler on line 332.

Example:

$db->setProfiler(new Zend_Db_Profiler_Firebug('DB Queries'));
$profiler = $db->getProfiler();

$channel = Zend_Wildfire_Channel_HttpHeaders::getInstance();
$channel->setRequest(new Zend_Controller_Request_Http());
$channel->setResponse(new Zend_Controller_Response_Http());

// Turn on profiling for local development
if ($xcart_http_host == 'localhost') {
    $profiler->setEnabled(true);
    $profiler->setFilterQueryType(Zend_Db_Profiler::INSERT |
                                  Zend_Db_Profiler::UPDATE);
}

$db->query("SELECT count FROM table1");