If you have used KiCad without crashes but it suddenly begins crashing try starting KiCad from a terminal window and see if it produces this kind of message:
Gdk-ERROR **: 11:37:33.424: The program 'kicad' received an X Window System error. This probably reflects a bug in the program.
Regardless of the blame on “the program”, this is more probably caused by the graphics drivers or something related to that. If something in the chain between the application and the hardware has been updated but the system not rebooted, the system may be in an inconsistent state and requires rebooting (or maybe at least restarting the graphical system).
(Updates without rebooting mostly work on Linux but it’s not 100% foolproof.)