[support] Session problems

Hello,

One of the clients using my site is complaining about the following problem:

"During a class, my students registered and logged onto their community accounts. When they started to explore it and look at the 'Buddies' section, the website seemed to show them a buddy list from a random student, not their own."

This is the "Buddies" plugin, running on Drupal 4.7. I first suggested that the previous pupil had not logged out properly, but the teacher confirmed that this wasn't the cause. This was the very first time that the students were logging into the system. Does anyone know what the problem might be?

Thanks.