Ubuntu 11.04 bug - Update Manager

When I logged in my Ubuntu, update manager window was popped up to ask for update. I clicked "Install Updates" button, but this time it said "waiting for apt-get to exit..." and then the window was dead. I closed all the other applications including firefox, terminal and editor, but the problem was not solved.

So I posted a bug report to the website. Someone suggested to restart virtual machine in order to solve it. Then I tried it. I did not know why my Ubuntu got this problem but this solution did work.

Good luck, Ubuntu!