I recall seeing something similar. Cannot recall where or when. I was unable to use LW 4.18 or 5 last year or first part of this year. I'd been using LW 4.16. I installed a 2nd OSX on a different drive & LW 5 runs fine there. Then one day not too long ago I gave LW 5 another go on my main OSX & it worked. It's my guess one of the OSX updates fixed something.
In your scenario, I'm wondering if that last Java update has somehow not installed as well as it should. One possibility is you download either the standalone Java installer & reinstall it, else the OSX Combo installer. The Java installer might tell you there's no update needed, I'm not sure.

Yes, I also have been thinking about a bad install, but everything seemed to go well and the installer program didn't mention any problem.
I try to do all the updates that Apple proposes via the automatical update system. The yesterday's update was only for Java but that's all I remember.
LW was turning during the download of this update. I had to reboot the computer after the Java install and, surprise, LW didn't launch no more ! Of course I tried to repare authorisations, check disk, check Java preferences... Nothing helped... So I deleted my LW Pro and tried, at your recommandation, the beta version 5.2.2 Basic. And that worked well. But I didn't hear anything else about this problem on other forums, so I think I might have an incomplete install ( which seems almost unbelievable) or some other problem which I still have to find. I hate unsolved problems...
Where can I drop my remarks about the beta version ?

Have a nice day !