a zombie process is a different thing. Zombie processes don't exist anymore,
and their memory has already been freed. The only thing left is the return
code, which the parent process can retrieve via C's wait(), waitpid() and
friends. As long as the father process doesn't recollect its dead children
(or terminates itself), those zombies will remain and, because they're no
real processes anymore, not respond to signals.
So summing up, this sounds like a bug in TkRemind... where exactly is
TkRemind? Could you name me the package? (I'd go look myself, but packages.d.o
is currently down...)