Is there a possibility of a security program on your computer that is preventing LW opening? Such as a spyware program or such. Some are not p2p program friendly & even when LW does not have spyware ... some say it does & stops them opening. Answer would be to put LW on its safe list.

Also, have you attempted running LW in a different account to see if it opens. Perhaps set up a test account. This might help show if the issue is account related.

I presume you tried deleting your LW preferences folder?

Did you upgrade to LW 5 from LW 4 or is LW 5 your first version?

Another alternative would be to downgrade back to LW 4. If you decide to do this, we'd highly recommend LW 4.16 rather than 4.18.