Repair permissions after installing. ie: Utilities -> Disk Utility. More efficient way of repairing permissions is via a safe boot. But no matter. Let us know how you get on.

If still problems, try setting up a Test account, easy & quick to do, then see if LW opens from there. Setting up a Test Account in OSX (click on link) (extra accounts are easy & quick to delete also, faster than setting them up in fact.)