I have an Ubuntu server running 8.04 in a school. It runs well for office personel and teachers. But I am having trouble with the lab applications. Students are k-6. When the students are playing games, some of the clients will freeze or crash. The system will then begin to slow down and clients have trouble logging out or running some apps. Eventually clients are unable to log in. Reboot of server clears the problem
I see segfaults in messages log and Kern.log. Sometimes the segfault will be nmapplett, sometimes npviewer.bin or tuxmath or gcompris. I have also had problems with cpu usage very high when running some games. Disabling audio in the apps helps them run better.

Does anyone know what might be causing this? What can I do or look at to get a better handle on the problem.

Thanks
Kraig