The FastCGI process exited unexpectedly / IIS7.5, PHP 5.2.17

Hi!

On my IIS 7.5 webserver some requests are not processed by the handler, IIS throws a 500 - Internal Server Error.

The case is the following:

With approx. 400 POST parameters the request is handled correctly and everything is fine.

With over 400, nearly 500 parameters the server throws 500 Error.

There is no clue in the log files, no error in the PHP logs, tried to expand the post_max_size, execution time etc. Nothing works, I'm out of ideas.

Thanks in advance,