Comment 55 for bug 515138

I have the same issue in my kubuntu 10.04 system, KDE version 4.4.2 .
I found that my issue may due to I'm using encrypted home directory. I used encryptfs bring by ubuntu. I found that each time when I'm doing login to my encrypted-home accounts, it left a [kded4] defunct process. When using su to this user and logout, it printed 'Sessions still open, not unmounting' .
I found that encryptfs used a pam plugin to function that auto mount/unmount home . In the pam config, there is line like

session optional pam_ecryptfs.so unwrap

When I commented these line out and login again, the defunct process went away. And when I uncommented them, the problem happened again.

Hope this information will help the debugging.