Hello!
Do not install the MRJ included with the LW installer that one did not work for me either for some reason.Instead go to Apple's web site and download the latest version which is 2.2.5 and work on all language versions of Mac OS 8.1X.Go to Apple's Knowledge database
Here!
And do a search for article id 75097(you have to click the expert search link to search for specific article id's) there you will find the download as well as information about MRJ.
When you have downloaded and installed it then run LW installer again but do not allow it to install MRJ instead choose no on that question.Now it should work.If not then also increase the installers preferred memory with about 50%.(Highlight the installer>go to File/show info/memory and here increase the preffered memory with 50%).If it still does not work then the installer must be corrupt.