Can you tell us your operating system version (windows 98, etc.), & types of firewalls you have, & also your connection devices brand names & model numbers (eg- D-Link 604G)

For now, may I recommend you update your version of Java to Java 1.4.2 (click on link) LW only asks for the minimum of Java 1.3 when it's installed but it needs later versions on some comp's to run properly. LW is designed using the latest Java & runs on Java so it's very important.