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When I run sudo apt-get update;sudo apt-get upgrade in Ubuntu 11.04, I get the exception below. VirtualBox is currently on '4.1.2'. I have installed apt-cacher-ng on this machine and install apt-get points locally.

W: Failed to fetch bzip2:/var/lib/apt/lists/partial/download.virtualbox.org_virtualbox_debian_dists_natty_contrib_binary-i386_Packages Hash Sum mismatch

praveensripati@MyMini:/etc/apt/apt.conf.d$ cat 01apt-cacher-ng-proxy  
Acquire::http { Proxy "http://localhost:3142"; };

What could be the reason for this?

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Where you getting VirtualBox from - Ubuntu,'s PPA, or from some other repository? – eug Oct 10 '11 at 15:40

As the error message says, the already known hash sum of the package mismatches the calculated one of the download.

You will have to discard the file and download it again.

Possible reasons:

  • Unreliable internet connection
  • 'Optimizing' internet service provider
  • broken network cable
  • hard disk failure.
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Try this in a Terminal (Dash->Terminal) window:

echo 'deb natty contrib' | sudo tee -a /etc/apt/sources.list
wget -q -O- | sudo apt-key add -
sudo apt-get update
sudo apt-get install virtualbox-4.1
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While not answering the original question ("Why is this?"), this looks like the solution to the problem. Good call lkjoel. – fixedit Oct 16 '11 at 0:06
Now that I see it, you could have just done a sudo apt-get update, and it should have fixed the problem. – MiJyn Oct 16 '11 at 21:09

Why don't you download the most recent version as a .deb-file from

together with the Extension Pack and install that? Will update your Virtualbox 'quite' easy.

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