You need to remove the java receipt files from the receipts folder. Receipts folder sample image. The receipt files are very important to retain normally, however if installation problems, that's the place to remove the specific items. Also see sample image below the one in link.

I have noticed "some" programs need special Leopard updates, but since LW has worked for at least many people, I am guessing the problem is java related. Particularly looking at the above report.

You can also try deleting the LW prefs folder "if" there is one. See bottom of the link page.

BTW how much spare disk space do you have on your system drive?
Which model computer are you using, cpu speed, how much ram, etc.?