One option to try for LW 5 is setting up a test account to see if the problem is account specific; Setting up a Test Account in OSX (click on link).

Make sure all your OSX updates are up to date. And do safe boot & repair permissions: SAFE Boot & Repair Permissions

Personally I had an issue of LW 5 not working in any account for about 4-5 months or so. Not sure how or why I was able to get it working whether it was an OSX update or reinstallation of OSX clean install after backing up all my files. Generally it's some kind of issue with Java being partly broken for some reason; perhaps with the original Java 6 installation.