Before you do re-install, do a
SAFE restart & Repair Permissions & re-install using the standalone Java installer. This can apparently fix some issues with Java (See
slin's
post & link to standalone Java installer) And then install LW & do another safe boot.
It's always good to repair your permissions with Disk Utility after a Safe restart both before & after you install software. Otherwise seemingly unknown errors can appear such as trying to launch the app. This combined process takes perhaps 15-25 mins. But it's worth the effort to be safe & keep your system healthy.