I had the same problem and manual edition of files '/var/lib/dpkg/status' and '/var/lib/dpkg/available' was very simple and worked fine. Just some more details:

Command 'sudo dpkg --listfiles' doesn't returns anything, except that 'oracle-jdk7-installer' wasn't installed.

I had to delete from both files the references to 'oracle-jdk7-installer'. For example, from /var/lib/dpkg/status, I deleted:

Code:
Package: oracle-java7-installer
Status: purge ok half-configured
Priority: optional
Section: non-free/java
Installed-Size: 81
Maintainer: Alin Andrei <webupd8@gmail.com>
Architecture: all
Version: 7u3-0~eugenesan~precise4
Replaces: icedtea-6-plugin, icedtea-7-plugin, openjdk-6-jdk, openjdk-6-jre, openjdk-6-jre-headless, openjdk-7-jdk, openjdk-7-jre, openjdk-7-jre-headless, oracle-jdk7-installer, sun-java6-bin, sun-java6-jdk, sun-java6-jre
Provides: default-jre, default-jre-headless, java-jdk, java-runtime, java-runtime-headless, java-virtual-machine, java2-jdk, java2-runtime, java2-runtime-headless, java5-jdk, java5-runtime, java5-runtime-headless, java6-jdk, java6-runtime, java6-runtime-headless, java7-jdk, java7-runtime, java7-runtime-headless, oracle-java7, oracle-java7-plugin, oracle-jdk7-installer
Depends: java-common (>= 0.24), locales, debconf (>= 0.5) | debconf-2.0
Pre-Depends: wget
Recommends: gsfonts-x11
Suggests: binfmt-support, ttf-baekmuk | ttf-unfonts | ttf-unfonts-core, ttf-kochi-gothic | ttf-sazanami-gothic, ttf-kochi-mincho | ttf-sazanami-mincho, ttf-arphic-uming, firefox | firefox-2 | iceweasel | mozilla-firefox | iceape-browser | mozilla-browser | epiphany-gecko | epiphany-webkit | epiphany-browser | galeon | midbrowser | moblin-web-browser | xulrunner | xulrunner-1.9 | konqueror | chromium-browser | midori | google-chrome
Conflicts: j2se-common, oracle-jdk7-installer
Description: Sun Java(TM) Development Kit (JDK) 7
 The JDK(TM) is a development environment for building and running
 applications, applets, and components using the Java programming language.
 .
 The JDK(TM) includes Java Runtime Environment (JRE) for running applications,
 Java Plug-in for running applets in web browsers and tools useful for
 developing and testing programs written in the Java programming language.
 .
 Note that this package does not contain any software from Oracle. This
 package does however contain a script to download and install Oracle JDK 7.
 All information regarding Java itself can be found on this website:
 http://www.oracle.com/
Homepage: http://www.oracle.com/technetwork/java/javase/downloads/index.html
Npp-Applications: ec8030f7-c20a-464f-9b0e-13a3a9e97384, 92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a
Npp-Mimetype: application/x-java-vm, application/x-java-applet, application/x-java-applet;version=1.1, application/x-java-applet;version=1.1.1, application/x-java-applet;version=1.1.2, application/x-java-applet;version=1.1.3, application/x-java-applet;version=1.2, application/x-java-applet;version=1.2.1, application/x-java-applet;version=1.2.2, application/x-java-applet;version=1.3, application/x-java-applet;version=1.3.1, application/x-java-applet;version=1.4, application/x-java-applet;version=1.4.1, application/x-java-applet;version=1.4.2, application/x-java-applet;version=1.5, application/x-java-applet;version=1.6, application/x-java-applet;jpi-version=1.6.0_07, application/x-java-bean, application/x-java-bean;version=1.1, application/x-java-bean;version=1.1.1, application/x-java-bean;version=1.1.2, application/x-java-bean;version=1.1.3, application/x-java-bean;version=1.2, application/x-java-bean;version=1.2.1, application/x-java-bean;version=1.2.2, application/x-java-bean;version=1.3, application/x-java-bean;version=1.3.1, application/x-java-bean;version=1.4, application/x-java-bean;version=1.4.1, application/x-java-bean;version=1.4.2, application/x-java-bean;version=1.5, application/x-java-bean;version=1.6, application/x-java-bean;jpi-version=1.7.0_03
Npp-Name: The Java(TM) Plug-in, Java SE 7
Sure, you have to edit files with su powers. For example:
Code:
$ sudo emacs /var/lib/dpkg/status