on KDE4 startup knotify call "/usr/local/bin/jackd -l" which is
meaningless because it only prints the default dir of jackd and
does not start any service;

the same is true for kbiff when mail arrives in the INBOX; to nail
this down (or at least to proof it), I substituted /usr/local/bin/jackd
with the following shell script:

#!/bin/sh
printf "new jackd call:\n" >> /tmp/jackd
echo $0 $* >> /tmp/jackd
/usr/local/bin/jackd.bin $* &
echo $! >> /tmp/jackd


and on KDE start or when a mail arrives the file /tmp/jackd shows:


new jackd call:
/usr/local/bin/jackd -l
39343
new jackd call:
/usr/local/bin/jackd -l
39345
new jackd call:
/usr/local/bin/jackd -l
39347


the PIDs of the zombies are always -1:

39342 2 Z 0:00,01 <defunct>
39344 2 Z 0:00,01 <defunct>
39346 2 Z 0:00,01 <defunct>

i.e. belong to the caller knotify or kbiff.

I first filed a bug in kde.org, see:
https://bugs.kde.org/show_bug.cgi?id=348841
but the folks @kde.org closed it again with the argument:
"...you should seek support from your distro, this is a configuration issue."