Which version of java are you using? 1.6.u1 causes problems for some people.
Try uninstalling your current version of java while LW is completely shut down. Go to the add/remove programs control panel and uninstall your current version of java. Now download and install
J2SE Runtime Environment (JRE) 5.0 Update 11(use the offline installer):
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11