php weird

Weird issue here. I'm running an internal office network. All employees are loging onto ubuntu desktops and our office server is on an ubuntu machine as well. Most users are having no issue, but when some of them access our php timeclock, firefox just crashes. Note that this is about five users. It's pretty regular. Most of them were able to get on it once and log in, but are now locked out (though a few never managed to get on).

Any thoughts as to why this might be?

x-posted to ubuntu_users