Using the Google Identity Toolkit SDK for Php with Google App Engine Launcher causes this error to appear. 'CGI / FastCGI has stopped working'.
As soon as you implement:
Gitkit_Client::createFromFile('/gitkit-server-config.json');
The crash will occur.
This is using the 1.9.30 version of Google App Engine Launcher that was recently released.
If you don't already have one, create a php.ini in the root of your project and add this line to enable the full version of curl.
extension = "php_curl.dll"
This solution has worked to resolve the error for me.