Maybe changing the compatibility mode might also have an effect. Right click the exe icon, go Properties>Compatibility and change it to Windows NT (or Windows 2000)
If not,....Uninstall LW and all Java versions on your system. Reboot and then download the JRE offline installer of the newest Java version from here:
http://java.sun.com/j2se/1.5.0/download.jsp
Install it and reboot again, then reinstall LW.