hello!
this bug you can reproduce:
see next code:
<?
$p = new pdf();

class pdf {
	function pdf() {
		$p = PDF_new();
		$opened = PDF_open_file ($p, "");
	}
}
?>
and ran it under IIS5. 
first time you get message about PDF_delete cannot be used in document scope
after reload a page you get violation access error.

but code as next:
<?
	$p = PDF_new();
	$opened = PDF_open_file ($p, "");
?>
working fine (gives error about PDF_Delete and don't hang IIS).
I'm purposely not write pdf_close, and pdf_delete functions
in my case, i would be sure, if some errors happens, IIS still live for any another request.
In case apache under linux, apaches child still lives and eat CPU and memory.

I cannot use CVS PHP versions. I can use only PHP releases.

vladimir.
Novosibirsk,
Russian Federation