Here is how to reproduce this bug:
 * Download http://fgouget.free.fr/bugs/testdep.tar.bz2
   This is a small archive that contains a set of test, empty, Debian package files along with their source.
   (run ./build to rebuild them)

 * Install the testdep-same_1.0-1_amd64.deb package.

 * Then run: qapt-deb-installer testdep-same-arch_1.0-1_i386.deb

qapt-deb-installer will then refuse to install the package with the following error:

    Status: Error: Cannot satisfy dependencies

Yet testdep-same-arch has 'testdep-same:amd64' as its sole dependency so the installed amd64 testdep-same package should satisfy it. Running dpkg confirms this:

$ sudo dpkg -i testdep-same-arch_1.0-1_i386.deb
Selecting previously unselected package testdep-same-arch.
(Reading database ... 214863 files and directories currently installed.)
Unpacking testdep-same-arch (from testdep-same-arch_1.0-1_i386.deb) ...
Setting up testdep-same-arch (1.0-1) ...

Finally, note that support for this type of dependency qualifier has been added in dpkg 1.16.5. For more details see:

* Bug #676232: dpkg: Please add support for specific arch qualifiers (cross-dependencies)
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=676232

* dpkg commit 7acf7afa581457bc2e9bd6cd1f442e6f45c1db29
  Author: Thibaut Girka <thib@sitedethib.com>
  Date: Thu Jun 28 01:11:11 2012 +0200

  Add support for specific arch-qualified dependencies

  This allows to use dependencies with arch-qualified package names. For
  example:

    Depends: libc6:amd64 (>= 2.14), libgcc1

  Closes: #676232

  Signed-off-by: Guillem Jover <guillem@debian.org>

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: qapt-deb-installer 2.0.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-26.38-generic 3.8.13.2
Uname: Linux 3.8.0-26-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.1
Architecture: amd64
Date: Sat Jul 27 01:02:52 2013
InstallationDate: Installed on 2013-04-29 (88 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
SourcePackage: qapt
UpgradeStatus: No upgrade log present (probably fresh install)

Reproducible: Always