Different to other release,the latest version of ubuntu Jaunty has a confirm dialog within 60 sec. when you logout,shutdown or restart. It prevents anyone to make a mistake,but anyway it may be excrescent for some people and  there is a easy way to disable it.

Right mouse click on the Switch users or shutdown area at right top,click Preferences

snapshot61

You will see following screen,unmark¬† the line which says “Show confirm dialogs for logout,restart and shutdown”and then close it,just so easy.

snapshot62

For ubuntu 9.10,read here.