Normally when a program is open an entry is placed on the taskbar in order to easily find it, which is useful when a lot of programs are open. In Ubuntu 10.04, when I moved a program to the other monitor (I'm using 2 monitors) the taskbar entry also moves to the taskbar on that monitor.
Now I switched over to Ultimate Edition, which is Ubuntu 10.04 with a lot of stuff added to it. When I drag a program to the other monitor, the entry in the taskbar disappears, but it does not reappear in the taskbar of the other monitor. So now the only way for me to find a program on this monitor if its hidden behind other windows is to use alt-tab.