Comment 1 for bug 159273

This bug still exists in Ubuntu Karmic Alpha 5, for Add/Remove Applications (gnome-app-install).

Steps to reproduce:

1. Open Add/Remove Applications.
2. Elect to search from "all available applications".
3. Search for "XChat IRC", for instance.
4. Place a tick next to "XChat IRC", to mark it for installation.
5. The Universe warning appears. Click Enable.
6. (Unexpected) The Universe warning appears again. Click Enable.

Disabling then re-enabling Universe via System/Administration/Software Sources does not retrigger this bug.
It only occurs once per boot, inside the LiveCD.