FastCGI Error Error Number: -2147467259 (0x80004005).是哪里的问题？

环境是windows 2003 IIS6 php5.3.29网站能打开，但是调用imagick的接口返回这个
FastCGI Error
The FastCGI Handler was unable to process the request.
Error Details:

The FastCGI process exited unexpectedly
Error Number: -2147467259 (0x80004005).
HTTP Error 500 - Server Error.
Internet Information Services (IIS)

以下是调用的代码
$im = new \Imagick();

$im->setCompressionQuality(80);

$im->readImage($pdf);//这里报错

foreach ($im as $k => $v) {
$v->setImageFormat('jpg');

$fileName = $k . '.jpg';
$savePath = $path . $fileName;

if ($v->writeImage($savePath) == true) {
$return[] = $fileName;
}
}

网上的方法都试过了，php.ini已经改过了，PHP目录权限，imagick和gs，temp目录的权限都已经改成network services和IUSER能运行读取和写入了，还是没用。