Proxy pac file not working IE10

Hi,

After updating IE9 to IE10 we have problems in implementing our proxy configuration via a proxy.pac file.

The same proxy.pac file workings without issues in IE9.

Here the content of my proxy.pac file :

function FindProxyForURL(url, host) {
	// If URL has no dots in host name, send traffic direct.
	if (isPlainHostName(host))
		return "DIRECT";

	// If specific URL needs to bypass proxy, send traffic direct.
	if (shExpMatch(url,"*.chet.local*"))
		return "DIRECT";

	// If IP address is internal or hostname resolves to internal IP, send direct.
	var resolved_ip = dnsResolve(host);

	if (isInNet(resolved_ip, "10.0.0.0", "255.255.0.0") ||
		isInNet(resolved_ip, "192.168.0.0",  "255.255.0.0") ||
		isInNet(resolved_ip, "127.0.0.1", "255.255.255.255") ||
		isInNet(host, "10.0.0.0", "255.255.0.0") ||
		isInNet(host, "192.168.0.0",  "255.255.0.0") ||
		isInNet(host, "127.0.0.1", "255.255.255.255"))
		return "DIRECT";

	// All other traffic uses below proxies, in fail-over order.
	return "PROXY forti.chet.local:8080";
}

Here the configuration of Group Policy Preferences :
http://www.world-lolo.com/images/uploads/image.num1393325521.of.world-lolo.com.png

The problem occurs when opening Internet Explorer after the opening of the session.
When we try to access the internet nothing happens and we have a 404 error.

If we go into the internet settings / proxy in internet explorer and that we close the window with the OK button without touching any settings. Internet works.

The problem reappears after the closing and opening of the session.

Thanks for your help...

Sincerely