If still doesn't work, then check the Java version that's running. If using OSX 10.5, then make sure Java is 'at least' Java 1.5. If it's already set to Java 1.5, then try Java 1.6 as that sorted the issue for at least one user;
Setting up Java 1.5. Good idea to log out & back in after doing this though.
If you are using OSX 10.4 then make sure it's running Java 1.5 since the newest LW versions will not run under Java 1.4
(Oh & the beta fixed it for someone too, however, beta versions may have bugs of their own.)
* Edit: Java preferences for Leopard OSX 10.5
