Comment 1 for bug 620956

I can reproduce this in the auto-upgrade testing setup. It appears the package did not have conffiles in
lucid but in maverick it does. That triggers a dpkg conffile prompt, here is the output with debug enabled:

Setting up ifupdown (0.6.10ubuntu2) ...
D000200: conffderef in='/etc/network/if-up.d/upstart' current working='/etc/network/if-up.d/upstart'

Configuration file `/etc/network/if-up.d/upstart'
 ==> File on system created by you or by a script.
 ==> File also in package provided by package maintainer.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.
*** upstart (Y/I/N/O/D/Z) [default=N] ?