cron.daily/apt fails every day on headless ubuntu server 12.04

[Stephen Hill]

/etc/cron.daily/apt:
verbose level 1
power status (255) undetermined, continuing
system is on main power.
sleeping for 25 seconds
power status (255) undetermined, continuing
system is on main power.
check_stamp: interval=86400, now=1357171200, stamp=1357084800, delta=86400 (sec)
apt-key net-update (failure)
download updated metadata (success).
send dbus signal (success)
check_stamp: interval=86400, now=1357171200, stamp=1357084800, delta=86400 (sec)
download upgradable (success)
check_stamp: interval=86400, now=1357171200, stamp=1357084800, delta=86400 (sec)
unattended-upgrade (success)
check_stamp: interval=432000, now=1357171200, stamp=1356825600, delta=345600 (sec)
autoclean (not run)
aged: ctime <30 and mtime <30 and ctime>2 and mtime>2
end remove by archive size: size=73564 < 512000

[Stephen Hill (steve-d-hill)]

 me@server:~$ sudo apt-key list
/etc/apt/trusted.gpg
--------------------
pub 1024D/437D05B5 2004-09-12
uid Ubuntu Archive Automatic Signing Key <email address hidden>
sub 2048g/79164387 2004-09-12

pub 1024D/FBB75451 2004-12-30
uid Ubuntu CD Image Automatic Signing Key <email address hidden>

pub 1024R/4C9D234C 2010-01-20
uid Launchpad webupd8

pub 4096R/C0B21F32 2012-05-11
uid Ubuntu Archive Automatic Signing Key (2012) <email address hidden>

pub 4096R/EFE21092 2012-05-11
uid Ubuntu CD Image Automatic Signing Key (2012) <email address hidden>

me@server:~$ sudo apt-key update
gpg: key 437D05B5: "Ubuntu Archive Automatic Signing Key <email address hidden>" not changed
gpg: key FBB75451: "Ubuntu CD Image Automatic Signing Key <email address hidden>" not changed
gpg: key C0B21F32: "Ubuntu Archive Automatic Signing Key (2012) <email address hidden>" not changed
gpg: key EFE21092: "Ubuntu CD Image Automatic Signing Key (2012) <email address hidden>" not changed
gpg: Total number processed: 4
gpg: unchanged: 4

[Daniel Hartwig (wigs)]

As the failing command is net-update, that output may be more useful:

$ sudo apt-key net-update

[Stephen Hill (steve-d-hill)]

I get zero output when I run this:

$ sudo apt-key net-update
$