Comment 5 for bug 605149

Actually, this rings a bell and I know what the problem is. cups-bsd.prerm executes update-inetd, which uses debconf. Normally, you can use debconf in child processes without a problem. However, because of some odd bits in the way the debconf shell and Perl bindings work together, if cups-bsd.prerm is being run from within something that uses debconf (debconf-apt-progress, in this case), IIRC the only way update-inetd is going to work properly is if cups-bsd.prerm sources the debconf confmodule; otherwise it will send debconf commands to the wrong place. I know this is a bit weird since cups-bsd.prerm doesn't itself use debconf directly.

In short, I think this will go away if you ensure that cups-bsd.prerm does '. /usr/share/debconf/confmodule' at the very top, immediately below 'set -e'. You'll need to test that, though.