There are many reasons for the runtime error, please ask your friend to check out this post http://lastchaos.aeriagames.com/forums/viewtopic.php?t=2164
and various other posts to see if any applies to them. If none applies, post the issue to this board and include all the details (e.g. your system, what you have tried and result, etc.) so that the community can try to help.
Hope you and your friends resolve the issue, and welcome to Last Chaos.