I'm seeing this on Lucid i386 with: $ apt-cache policy apt-cacher apt-cacher: Installed: 1.6.10ubuntu1 Candidate: 1.6.10ubuntu1 Version table: *** 1.6.10ubuntu1 0 500 http://gb.archive.ubuntu.com/ubuntu/ lucid/universe Packages 100 /var/lib/dpkg/status $ sudo apt-get update Hit http://gb.archive.ubuntu.com lucid Release.gpg Hit http://gb.archive.ubuntu.com/ubuntu/ lucid/main Translation-en_GB ... Hit http://gb.archive.ubuntu.com lucid-updates/multiverse Packages Hit http://gb.archive.ubuntu.com lucid-updates/multiverse Sources Fetched 11.0MB in 1min 6s (167kB/s) Reading package lists... Done W: GPG error: http://gb.archive.ubuntu.com lucid Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key In /var/log/apt-cache/error.log I see: Mon Apr 12 22:31:14 2010|info [1112]: ALARM! /var/cache/apt-cacher/packages/gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg file size mismatch (found 0, expected 189). Renaming to /var/cache/apt-cacher/packages/gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg.corrupted. $ ls -lstr /var/cache/apt-cacher/packages/gb*Release.gpg* 4 -rw-r--r-- 1 www-data www-data 189 2010-04-08 00:07 /var/cache/apt-cacher/packages/gb.archive.ubuntu.com_ubuntu_dists_lucid-updates_Release.gpg 4 -rw-r--r-- 1 www-data www-data 189 2010-04-10 06:00 /var/cache/apt-cacher/packages/gb.archive.ubuntu.com_ubuntu_dists_lucid-proposed_Release.gpg 4 -rw-r--r-- 1 www-data www-data 189 2010-04-12 22:31 /var/cache/apt-cacher/packages/gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg.corrupted In /var/log/apt-cache/access.log I see: $ grep 'gb\.archive.*Release\.gpg' /var/log/apt-cacher/access.log Thu Apr 8 00:07:31 2010|10457|10.254.251.51|MISS|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Thu Apr 8 00:07:37 2010|10457|10.254.251.51|MISS|189|gb.archive.ubuntu.com_ubuntu_dists_lucid-updates_Release.gpg Thu Apr 8 01:23:55 2010|10573|10.254.251.74|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Thu Apr 8 07:57:57 2010|11032|10.254.251.51|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Thu Apr 8 20:26:28 2010|11328|10.254.251.74|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Fri Apr 9 07:45:59 2010|11866|10.254.251.51|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Fri Apr 9 21:10:46 2010|12182|10.254.251.51|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Sat Apr 10 06:00:43 2010|12815|10.254.251.95|EXPIRED|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Sat Apr 10 06:00:49 2010|12815|10.254.251.95|MISS|189|gb.archive.ubuntu.com_ubuntu_dists_lucid-proposed_Release.gpg Sat Apr 10 06:01:32 2010|12858|10.254.251.74|HIT|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Sat Apr 10 06:08:45 2010|12980|10.254.251.51|HIT|189|gb.archive.ubuntu.com_ubuntu_dists_lucid_Release.gpg Mon Apr 12 15:37:10 2010|15736|10.254.251.51|HIT|189|gb.archive.ubuntu.com_ubuntu_dists_lucid-updates_Release.gpg Mon Apr 12 22:31:15 2010|1183|10.254.251.2|HIT|189|gb.archive.ubuntu.com_ubuntu_dists_lucid-updates_Release.gpg