How curious! I wonder if you two are playing on identical Windows XP machines??
Write to Amanita Design support and besides telling them what version of XP you're using (Home or Professional) be sure to also mention what kind of computer you're playing on (such as Dell laptop or Alien tower, etc.) as that may have something to do with the problem.
You'll find a "Contact Support" form at the bottom of the
About page. Add the link to this topic in your message(s) so that they can see the error with their own eyes. (here it is:
http://forum.amanita-design.net/index.php?topic=5171.msg15601#msg15601 )
And please post a follow up when a solution is found.
~Alex