Comment 2 for bug 561751

I can replicate this.

$ sudo apt-get install clamav-milter
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  daemon
The following NEW packages will be installed:
  clamav-milter
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 323kB of archives.
After this operation, 680kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu/ lucid/universe clamav-milter 0.96+dfsg-1ubuntu1 [323kB]
Fetched 323kB in 1s (300kB/s)
Preconfiguring packages ...
Selecting previously deselected package clamav-milter.
(Reading database ... 60741 files and directories currently installed.)
Unpacking clamav-milter (from .../clamav-milter_0.96+dfsg-1ubuntu1_i386.deb) ...
Processing triggers for ureadahead ...
Processing triggers for man-db ...
Setting up clamav-milter (0.96+dfsg-1ubuntu1) ...
dpkg: error processing clamav-milter (--configure):
 subprocess installed post-installation script returned error exit status 20
E: Sub-process /usr/bin/dpkg returned an error code (1)