packages.gz corrupt -- cannot fully install krb5 security update

Workaround.

wget http://security.ubuntu.com/ubuntu/dists/dapper-security/universe/binary-i386/Packages.bz2
bunzip2 Packages.bz2
sudo mv Packages /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_dapper-security_universe_binary-i386_Packages
sudo apt-get install krb-user

Correction. Last command is:

sudo apt-get install krb5-user

Thanks for the report, however I cannot reproduce this. Can you re-check your "apt-get update"? I had no problems installing from the archives.

$ sudo apt-get update
Get:1 http://security.ubuntu.com dapper-security Release.gpg [191B]
Get:2 http://us.archive.ubuntu.com dapper Release.gpg [189B]
Hit http://security.ubuntu.com dapper-security Release
Hit http://us.archive.ubuntu.com dapper Release
Hit http://security.ubuntu.com dapper-security/main Packages
Hit http://us.archive.ubuntu.com dapper/main Sources
Hit http://security.ubuntu.com dapper-security/restricted Packages
Ign http://security.ubuntu.com dapper-security/universe Packages
Hit http://us.archive.ubuntu.com dapper/restricted Sources
Hit http://us.archive.ubuntu.com dapper/universe Sources
Hit http://security.ubuntu.com dapper-security/multiverse Packages
Hit http://us.archive.ubuntu.com dapper/multiverse Sources
Get:3 http://security.ubuntu.com dapper-security/universe Packages [77.5kB]
99% [3 Packages gzip 0] [Connecting to archive.ubuntu.com (91.189.89.8)]
gzip: stdin: not in gzip format
Err http://security.ubuntu.com dapper-security/universe Packages
  Sub-process gzip returned an error code (1)
Get:4 http://archive.ubuntu.com dapper-updates Release.gpg [191B]
Get:5 http://archive.ubuntu.com dapper Release.gpg [189B]
Hit http://archive.ubuntu.com dapper-updates Release
Hit http://archive.ubuntu.com dapper Release
Hit http://archive.ubuntu.com dapper-updates/main Packages
Hit http://archive.ubuntu.com dapper-updates/restricted Packages
Hit http://archive.ubuntu.com dapper-updates/universe Packages
Hit http://archive.ubuntu.com dapper-updates/multiverse Packages
Hit http://archive.ubuntu.com dapper/main Packages
Hit http://archive.ubuntu.com dapper/restricted Packages
Hit http://archive.ubuntu.com dapper/universe Packages
Hit http://archive.ubuntu.com dapper/multiverse Packages
Fetched 5B in 3s (1B/s)
Failed to fetch http://security.ubuntu.com/ubuntu/dists/dapper-security/universe/binary-i386/Packages.gz Sub-process gzip returned an error code (1)
Reading package lists... Done
E: Some index files failed to download, they have been ignored, or old ones used instead.

I have tested with:

curl -s http://91.189.89.8//ubuntu/dists/dapper-security/universe/binary-i386/Packages.gz | gunzip -c >/dev/null

And got no errors. Perhaps there is a transparent proxy between you and the internet that is breaking this file?

I'm not sure what gets in /var/lib/apt/lists/partial, but a dapper-security universe file was there and clearing it seems to have solved the problem.