Loss of Interrupt Capability

[The Mad Hacker]

This is probably a dumb question but, here goes anyway.
Recently, two of our UNIX PCs, one a 3.0 and one a 3.5,
no longer recognize the DELETE key as an interrupt, but
only for some programs (e.g., cat, cpio).  On other
programs DELETE interrupts just fine.  When I do an
stty -a, it insists that intr = DEL, and both systems
pass the diagnostic disk's keyboard test.  While I could
live without an interrupt character, it would be painful!

HELP!  Any ideas about what could be wrong and how to fix
this?  Thanks in advance.