"Scan popup" in Gnome 3

[xzy3186]

Hi, I am a Ubuntu 11.04 user. These days I upgraded my desktop from gnome 2 to gnome 3. Then I found the "scan popup" function could not work properly. On gnome 3 the "popup" window would not appear after selecting a word on the screen. However it worked perfectly on gnome 2. So I wonder if there are some modifications in the clipboard of gnome 3. Is there anyone have solutions?