First, make sure that you have the most recent version of Stuffit Expander, which I believe is 6.5.1. We are continuing to work with ZeroG on this problem. You also might want to try our smaller download that does not include the MRJ (since you already installed that successfully, even though the rest of the first install failed). You can download it from:

http://www.limewire.com/index.jsp/download_other

Thanks.