Hod to Select Default Dislay Manager Desktop Environments Question

I've tried to reinstall GNOME because it's not fully functional. When I do: "sudo aptitude install ubuntu-desktop," I get the message below. I can see the *init.d script but I'm afraid to touch it. How can I resovle this prolem? T 1f40 he <Ok> at the bottom is not clickable. I would expect it to bring up an edit screen or something but it doesn't.

HTML Code:

   ┌────────────────────────────┤ Configuring gdm ├────────────────────────────┐
 │                                                                           │
 │ A display manager is a program that provides graphical login              │
 │ capabilities for the X Window System.                                     │
 │                                                                           │
 │ Only one display manager can manage a given X server, but multiple        │
 │ display manager packages are installed.  Please select which display      │
 │ manager should run by default.                                            │
 │                                                                           │
 │ (Multiple display managers can run simultaneously if they are configured  │
 │ to manage different servers; to achieve this, configure the display       │
 │ managers accordingly, edit each of their init scripts in /etc/init.d,     │
 │ and disable the check for a default display manager.)                     │
 │                                                                           │
 │                                  <Ok>                                     │
 │                                                                           │
 └───────────────────────────────────────────────────────────────────────────┘