Try setting up a Test account, see if LW will open within it. If yes, then the issue is something to do with your main account. Setting up a new account is not difficult & not difficult to later remove via control panel.

Which version of LW were you using before this one?
I guess you have tried setting LW to run as admin?
Which security programs do you have on your computer. You may need to manually add LW to your firewall exceptions, removing the older one. Not that this should necessarily apply to your problem, but same might apply to other security software.