HTTPRequest() fails when the same URL works in browser

We've been struggling with some URLs which just do not work in Windev 14 and now 15 which work perfectly for all webbrowsers. I've contacted the Patrick at the helpdesk, but he couldn't immediately reproduce the issue - which is *also* what we see with our customers. The URL which doesn't work for us, does sometimes work for some customers... very frustrating. So I'm looking for some more data... I'd like you to run the following snippet of code and post the result here:

rpt is string

HTTPTimeOut(10) // I don't want you waiting 30 seconds

FOR EACH STRING url OF "http://unitas.nl/rss.xml http://douane.nl/rss/douane-serviceberichten.xml"; SEPARATED BY " "

	IF HTTPRequest(url) THEN	

		rpt+=StringBuild("Request to %1 worked. %2 bytes received.", url, Length(HTTPGetResult()))+RC

		FOR EACH STRING s OF HTTPGetResult(httpHeader) SEPARATED BY RC

			IF s[="X" OR s[="Proxy" THEN rpt+=s+RC

		END

	ELSE

		rpt+=StringBuild("FAILED: Request to %1.", url)+RC

	END

END

ToClipboard(rpt)

Info(rpt, "The above text is now on your clipboard, please paste your result on the forum.")

The first URL, which is our own server, always works. The second one usually doesn't work. Which is why I set the timeout to a short time. When it does work for our customers, they generally have a proxy server installed. Which is what this piece of code is trying to detect with the inner for each loop.

The second URL is just an example, I'm seeing this behaviour with more servers. The douane.nl one is an IBM webserver, there must be more of those out there.