First it is a 405. Next given the detail you have posted how the hell should we know? Can you get the same page with a browser? Can you get any pages with your LWP implementation? If you can do both, and you have tried using GET and POST try adding:

my $ua = new LWP::UserAgent;
$ua->agent("User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows 98;
+ )"); # Lie :-)
[download]

If it still fails try adding cookie support (see the docs). Use Data::Dumper to have a look at what is happening inside LWP by dumping the response object. You may see the cookie being set that you are not sending back or javascript widgets or....