When performing a zone delegation I receive an Internal Server Error, but the error comes with the nice NicTool CSS and the delegation is actually performed. This is only a periodic task for us, so I haven't looked into it further. The logs report:
[Tue Sep 15 03:39:18 2009] [error] Can't locate object method "_close_window" via package "ModPerl::Registry"
at /var/www/localhost/NicToolClient/htdocs/delegate_zones.cgi line 96.\n
I'm guessing that it's supposed to close the browser window, and since it doesn't actually fail in the delegation, it's a low-priority bug.