For Vista ... actually I think it may need java 1.6 but not to completely change advice, check options 5 & 6 in Fixes for LW. They also can play a surprisingly major role. Also, try setting up a test account on your computer with admin abilities, then try opening LW from there.

If all that doens't work ... then try this version -> Welcome, MiHD.net - World's most generous file web hosting service
Careful which links you click .. initially the one on top left, then far right on 2nd window.
You can before doing that go to Start menu -> Programs -> LW -> Uninstall.

OH sorry that is the basic version ... but make sure it works ... if so then let us know.

Edit: It is ALWAYS reccommended to delete your LW prefs folder if upgrading to PRO.