Red Error sign when opening update manager

Question

When I open update manager it runs for a brief second then a red stop sign appears with no comments. I click close on the sign and update manager closes.

Answer 1

Judging by the description of the sign you gave it seems to be the broken repository sign. Here is how to fix this.

Click on the sign and select "Check for updates". Keep that window open. This will fail if the problem lies here. Now, open the software center and go to edit>software sources. In the other software tab, disable the checkboxes next to the names of the repositories that failed to work (from the check for updates window). Then, update as normal.

Answer 2

Open terminal and type the following command:

sudo rm /var/lib/apt/lists/* -vf

Press enter. Then type:

sudo apt-get update