Bug with characters display in published storyline

Hi, 

We have a big problem here. We delivered  3 elearning courses yesterday to a client. The courses where tested, and fully fonctionnal.  

BUT, today, the client called us in panic. Here's what he saw on his system (HP Elite book)All 3 modules show the same thing : all letters are in a mess.

We can't reproduce this bug on our systems, and we don't understand where it come from. 

Please, this is urgent. Need help !