installing clamav

I attempted to install clamav without success. Here is the screen output.

$ sudo add-apt-repository ppa:ubuntu-clamav/ppa;
password requested by system
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver hkp://keyserver.ubuntu.com:80/ --recv F80220D0E695A455E651AC4D8AB767895ADC2037
gpg: requesting key 5ADC2037 from hkp server keyserver.ubuntu.com
gpg: key 5ADC2037: public key "Launchpad PPA for Clamav Update Team" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
palaymic@melmick-P4M800-8237:~$ sudo apt-get update
Ign http://extras.ubuntu.com natty InRelease
Ign http://archive.canonical.com natty InRelease
Ign http://us.archive.ubuntu.com natty InRelease
Ign http://us.archive.ubuntu.com natty-updates InRelease
Ign http://us.archive.ubuntu.com natty-security InRelease
Ign http://ppa.launchpad.net natty InRelease
Hit http://extras.ubuntu.com natty Release.gpg
Hit http://archive.canonical.com natty Release.gpg
Hit http://us.archive.ubuntu.com natty Release.gpg
Get:1 http://ppa.launchpad.net natty Release.gpg [316 B]
Hit http://extras.ubuntu.com natty Release
Hit http://archive.canonical.com natty Release
Hit http://us.archive.ubuntu.com natty-updates Release.gpg
Get:2 http://ppa.launchpad.net natty Release [9,748 B]
Hit http://extras.ubuntu.com natty/main Sources
Hit http://archive.canonical.com natty/partner i386 Packages
Hit http://us.archive.ubuntu.com natty-security Release.gpg
Hit http://extras.ubuntu.com natty/main i386 Packages
Ign http://extras.ubuntu.com natty/main TranslationIndex
Ign http://archive.canonical.com natty/partner TranslationIndex
Hit http://us.archive.ubuntu.com natty Release
Get:3 http://ppa.launchpad.net natty/main Sources [1,866 B]
Hit http://us.archive.ubuntu.com natty-updates Release
Get:4 http://ppa.launchpad.net natty/main i386 Packages [2,002 B]
Ign http://ppa.launchpad.net natty/main TranslationIndex
Hit http://us.archive.ubuntu.com natty-security Release
Hit http://us.archive.ubuntu.com natty/main Sources
Hit http://us.archive.ubuntu.com natty/restricted Sources
Hit http://us.archive.ubuntu.com natty/multiverse Sources
Hit http://us.archive.ubuntu.com natty/restricted i386 Packages
Hit http://us.archive.ubuntu.com natty/multiverse i386 Packages
Ign http://us.archive.ubuntu.com natty/main TranslationIndex
Ign http://us.archive.ubuntu.com natty/multiverse TranslationIndex
Ign http://us.archive.ubuntu.com natty/restricted TranslationIndex
Ign http://us.archive.ubuntu.com natty/universe TranslationIndex
Hit http://us.archive.ubuntu.com natty-updates/main Sources
Hit http://us.archive.ubuntu.com natty-updates/restricted Sources
Hit http://us.archive.ubuntu.com natty-updates/universe Sources
Hit http://us.archive.ubuntu.com natty-updates/multiverse Sources
Hit http://us.archive.ubuntu.com natty-updates/main i386 Packages
Hit http://us.archive.ubuntu.com natty-updates/restricted i386 Packages
Hit http://us.archive.ubuntu.com natty-updates/universe i386 Packages
Hit http://us.archive.ubuntu.com natty-updates/multiverse i386 Packages
Ign http://us.archive.ubuntu.com natty-updates/main TranslationIndex
Ign http://us.archive.ubuntu.com natty-updates/multiverse TranslationIndex
Ign http://us.archive.ubuntu.com natty-updates/restricted TranslationIndex
Ign http://us.archive.ubuntu.com natty-updates/universe TranslationIndex
Hit http://us.archive.ubuntu.com natty-security/main Sources
Hit http://us.archive.ubuntu.com natty-security/restricted Sources
Hit http://us.archive.ubuntu.com natty-security/universe Sources
Hit http://us.archive.ubuntu.com natty-security/multiverse Sources
Hit http://us.archive.ubuntu.com natty-security/main i386 Packages
Ign http://extras.ubuntu.com natty/main Translation-en_US
Hit http://us.archive.ubuntu.com natty-security/restricted i386 Packages
Hit http://us.archive.ubuntu.com natty-security/universe i386 Packages
Hit http://us.archive.ubuntu.com natty-security/multiverse i386 Packages
Ign http://us.archive.ubuntu.com natty-security/main TranslationIndex
Ign http://us.archive.ubuntu.com natty-security/multiverse TranslationIndex
Ign http://us.archive.ubuntu.com natty-security/restricted TranslationIndex
Ign http://extras.ubuntu.com natty/main Translation-en
Ign http://archive.canonical.com natty/partner Translation-en_US
Ign http://us.archive.ubuntu.com natty-security/universe TranslationIndex
Ign http://archive.canonical.com natty/partner Translation-en
Get:5 http://us.archive.ubuntu.com natty/universe Sources [5,430 kB]
Ign http://ppa.launchpad.net natty/main Translation-en_US
Get:6 http://us.archive.ubuntu.com natty/main i386 Packages [1,987 kB]
Ign http://ppa.launchpad.net natty/main Translation-en
Get:7 http://us.archive.ubuntu.com natty/universe i386 Packages [7,755 kB]
Ign http://us.archive.ubuntu.com natty/main Translation-en_US
Ign http://us.archive.ubuntu.com natty/main Translation-en
Ign http://us.archive.ubuntu.com natty/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com natty/multiverse Translation-en
Ign http://us.archive.ubuntu.com natty/restricted Translation-en_US
Ign http://us.archive.ubuntu.com natty/restricted Translation-en
Ign http://us.archive.ubuntu.com natty/universe Translation-en_US
Ign http://us.archive.ubuntu.com natty/universe Translation-en
Ign http://us.archive.ubuntu.com natty-updates/main Translation-en_US
Ign http://us.archive.ubuntu.com natty-updates/main Translation-en
Ign http://us.archive.ubuntu.com natty-updates/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com natty-updates/multiverse Translation-en
Ign http://us.archive.ubuntu.com natty-updates/restricted Translation-en_US
Ign http://us.archive.ubuntu.com natty-updates/restricted Translation-en
Ign http://us.archive.ubuntu.com natty-updates/universe Translation-en_US
Ign http://us.archive.ubuntu.com natty-updates/universe Translation-en
Ign http://us.archive.ubuntu.com natty-security/main Translation-en_US
Ign http://us.archive.ubuntu.com natty-security/main Translation-en
Ign http://us.archive.ubuntu.com natty-security/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com natty-security/multiverse Translation-en
Ign http://us.archive.ubuntu.com natty-security/restricted Translation-en_US
Ign http://us.archive.ubuntu.com natty-security/restricted Translation-en
Ign http://us.archive.ubuntu.com natty-security/universe Translation-en_US
Ign http://us.archive.ubuntu.com natty-security/universe Translation-en
Fetched 13.9 kB in 6s (2,219 B/s)
W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_universe_source_Sources Hash Sum mismatch

W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages Hash Sum mismatch

W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_universe_binary-i386_Packages Hash Sum mismatch

E: Some index files failed to download. They have been ignored, or old ones used instead.
palaymic@melmick-P4M800-8237:~$ sudo apt-get -y install clamav clamavtk
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package clamavtk

I have also looked at documentation and see there is also an avast virus protection for linux. Are there any major differences between these two? The system only has linux on it. My laptop has windows Vista and Linux. I am supremely satisfied with the windows virus protection. I don't want the package to conflict with the one I already use for Windows.