function releaseMutex($filename) {
		$ret = flock($this->fplock[md5($filename)], LOCK_UN);
		fclose($this->fplock[md5($filename)]);
		unset($this->fplock[md5($filename)]);
		if (! $ret) {
			$this->debug("Not able to release lock for $filename");
		}
		return $ret;
	}