Hugbug,
This is a real strange one because after the segfault, it starts up. with ulimit set to unlimited it'll even drop a core file on both nzbget -D or nzbget -S. But the service is still running (so maybe the segfault is happening on one of the closing parent processes when you fork() ?
I'll PM you the core dump file if it's any use to you, otherwise things 'appear' to be working. Before i fully package your app and share it with all Fedora/RedHat/CentOS users (via RPM and nuxref), i just want to iron this out with you if possible. i wouldn't want some systems to drop a core file each time it starts up.
I don't mind making a small patch file on my end if necessary (no need to recreate a new build if we figure this out).
Update: Hugbug was once again a hero and solved the problem here.