Unable to view presentations in ILS with multiple users connected

I am using Windows XP, and I know that it has a very good built-in ILS in it. I also have already developed a training content using Powerpoint. NetMeeting is already opened and my participants are already connected to the ILS. The problem is that during the digital web conferences. One of my users could not see the presentation. I did a run through though before starting. I have found out that when she is the sole person connected through the ILS, she could view the presentation, but if there are others already present with her, it’s like the presentation is being blocked from her. What could I possibly advice her to do?
