Memory Fault - Core Dumped

I use SCO UNIX 5.07 on a Compaq Proliant Machine. Each time I press the Escape or Delete key while running a program or issuing a FoxBase+ command from the dot prompt, I receive the error message: "Memory Fault - Core Dumped" and the screen locks up immediately.

I would appreciate if necessary solution could be kindly provided, please.

Thank you.