Stuck in a Rut!

Hello- first post from a middle school tech teacher..
I bought a used probotix comet for use in my classroom. It came with a controller and a computer to run it.
The software worked initially- as I was able to move the machine around some (x,y, and z) but now Linux crashes everytime it runs..
Does anybody have any thoughts that would help.
Appreciate it.

We need more information.
Could you post what the error messages are when Linuxcnc shuts down? (it isn't "crashing")

Most likely it is some kind of a configuration error, or it may be detecting a hardware problem.