Sounds like a JAVA issue. Uninstall LW and all Java versions on your computer. Then download the JRE offline installer of the newest Java version here:
http://java.sun.com/j2se/1.5.0/download.jsp
Install that version manually (i.e. using the offline installer .exe) and then reinstall LW.
If that doesn't solve your problem, check any AV program or Anti spyware program on whether they see LW as a threat and block it from opening.