Is "dpkg -i" fatal to apt-get? [ Was: Re: Refetching an installed package, lost from /var/cache/apt/archives/?]

[Erik Christiansen]

After a successful install, using:

dpkg -i /var/cache/apt/archives/libborqt_6.9.0-3_i386.deb

all applications worked fine for many weeks, but apt-get was not too
happy, when subsequently asked to install something unrelated:

The following packages have unmet dependencies:
  libborqt: Depends: xlibs (> 4.1.0) but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

What has cleared it, is invoking "apt-get -f install" _twice_.

If this results from a cumulative re-ordering of the dependency data,
then it might be generally helpful to hint at reiteration in the error
message.

Erik