When you try to detach a tab in a window with only 1 tab (right click tab -> detach), the application will crash. Best way to work around this is to insensitive the detach option in the tab-menu when there is only 1 tab opened, like in the file menu.
Fixed with revision 24238. 2007-01-02 Benedikt Meurer <benny@xfce.org> * terminal/terminal-window.c(terminal_window_detach_screen): Do not crash when you try to detach the first tab with MiscAlwaysTabs is set to TRUE. Bug #2686.