That second Netscape URL returns a 404 response when I hit it through a browser, and a 404 response when I hit it through LWP. The responses are different, which could be attributable to one of several things:

• The site is looking for a cookie.
• The site is decoding the agent string.
• The site is making a decision based on some other part of the HTTP request header.

Without a lot of experimenting, it's hard to tell which.

Update: You've correct the second URL. That one does work for me. You might be having an issue with your proxy server.