1. Try deleting your LW Preferences folder whilst LW is
closed; instructions here:
Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.)
2. If that doesn't help, make sure you configured your XP firewall to allow LW full access:
Firewall configuration instructions (click on link)
If still no good, then port forwarding is probably the way to go.
3. Your model is the Speedstream 5200 right? Most important step in doing this is the very first one which is
setting up a static ip (click on link). Then see
Port Forwarding for the Efficient(Siemens) Speedstream 5200