You may ask why i am still running LW Pro 4.12.6??
answer is it does what i need and i am too stingy to upgrade to a "newer, more elaborate version" 50 bucks or so for a 1 year subscription, you are kidding??
Anyway, i recently noticed (yesterday) that LW Pro 4.12.6 would no longer open. The only thing i could remember installing in the last month or 2 was a Java update. It turns out i was now running Java 6 update 20.
I decided to uninstall this update from the add/remove programs, it rolled me back to Java version 6 update 7 and sure enough good old LW 4.12.6 kicked back into life and now opens everytime.
I thought this might assist others using old LW and running Java v6 update 20.

Thanks for the heads up mrekul. Often been an issue for many years that one version of Java suits some people but does not work well for the occasional other person. And sometimes there's simply been an unreliable version of Java for many people who use LW.