Yes, I'm able to get to the page via Safari or Firefox and I can curl the page from the command line when I'm getting the http 500 invalid message. But, you may be on to something. I moved the machine to another subnet, got a new ip address and it immediately worked again without the 500 error. Strange that I can load it via a browser and can get the url with other tools, but it's intermittent with LWP.