Welcome to the monastery, {if you haven't already been :)}

While I have no experience coding LWP it would seem to me that either the POST or GET method is not being allowed on this server. Also you may want to state explicitly which line causes the error, so you could see which method it was not taking a liking to.

Have you tried this on a website you own (assuming this one is not run by you)? even one setup on your local machine via Apache/IIS would be sufficient.. can you pull data there? My first step of debugging (with no LWP exp as stated) would be to see if I or the site in question is the problem. Try it on a site of your own to see if you have a malformed request. If it works there, then it may be something with the site you are requesting from

Just my thoughts,