What version of Java are you using? You can either update to the latest version here (I have this one & LW's working fine): Java SE Downloads
or try this older version, which has worked well for lots of people: Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11
Whichever Java version you use, download the JRE offline installer & remove any other Java versions before installing another one.

If you're already using Java 1.6.0_03 (the latest one) then try that older version instead.