Since I upgraded to Ubuntu 8.04, I had noticed that Update Manager was hanging, but not bothered to look into fixing it.
Last month I upgraded my notebook from Ubuntu 7.10 to 8.04 (”Hardy Heron”). Since then, whenever I tried tried to install the up to 133 updates that had become available, the Update Manager would hang indefinitely instead of prompting me for the user password.
If you’re in the same situation, the following tips might help you. Edit /etc/hosts with an editor of your choice (e.g. sudo vi /etc/hosts). There should be two entries with IPv4 addresses starting with 127.0.x.x, like this:
Remove the domain name from the entry starting with 127.0.1.1, leaving only the computer name and save the file. Now try again.
When I made this change I got the password prompt as expected and all the updates where downloaded and applied.