II gs can't load ProDOS... HELP!!!

[pweber@cyclops.pei.edu (Paul Weber)]

I'm an IBM person teaching in a school with a bunch of IIgs's.  I'm not 
prejudiced, just ignorant.  

All of a sudden I have a IIgs that can't load the ProDOS from the 
AppleWorks disks.  Any of them.  I've swapped every component except the 
keyboard and mouse.  I tried the system startup disk, same problem.  I 
tried AppleWorks 4, same problem.  I tried the Apple Tour, works fine!\

Any ideas?

Thanx,

Teacher in distress
Paul Weber
pweber@cyclops.pei.edu