samhuri.net/public/posts/2006/04/zsh-terminal-goodness-on-os-x.html.md

Apple released the OS X 10.4.6 update which fixed a really annoying bug for me. Terminal (and iTerm) would fail to open a new window/tab when your shell is zsh. iTerm would just open then immediately close the window, while Terminal would display the message: [Command completed] in a now-useless window.

Rebooting twice to get the fix was reminiscent of Windows, but well worth it.