This happens *sometimes* with some apps like devhelp and *always* with other ones like anjuta. 4.4.x panel launcher had not such problem.
*** This bug has been marked as a duplicate of bug 3889 ***
Err plugins, launchers, meh...
hmm I don't know if this bug is the same of the 3889. This one is about external programs, launched by a panel launcher, that stay in zombie status after exit, and it's still present in version 4.5.91-rev28292. The fix used for bug 2983, related to thunar/xfdesktop, should work if applied to plugins/launcher/launcher-exec.c although I still didn't test it properly.
I undid the dupplicate within 20 seconds, will look into it.
ok, that patch seems to work to me.
Fixed in revision 28562. I really though is picked the patch from Thunar, but i didn't...