Make sure that the XP firewall's off & that the Trend Micro firewall's configured to allow LW (click below).
PortForward.com - Free Help Setting up Your Router or Firewall

Update your Java to this version. Download the offline installer & remove any other Java versions before you install this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

If the page can't be displayed, it's not a good sign...something may be blocking LW's default port - possibly your ISP. Do you know anyone who uses the same ISP & can use p2p without a problem? Try changing ports. In LW tools > options > advanced > firewall config. Change LW's listening port to 64049 (or try others in the range of 49152-65535) > Apply > ok.

There's a firewall within your modem, try port forwarding. The instructions are here.
Port Forwarding for the Motorola SBG 900
Don't forget to set up a static IP address first (there's info about that in those instructions). LW's listening port, port in the 'manual port forward' box & port forwarded within the modem should all be the same number.