I recently installed a package from a ppa on Ubuntu 12.04 beta, but apparently it didn't work out, and now it is giving me errors at every update or install I make, even after deactivating the ppa from my sources.

This is what I get when I try uninstalling from USC:

      installArchives() failed: (Reading database ...  
    (Reading database ... 5% 
    (Reading database ... 10% 
    (Reading database ... 15% 
    (Reading database ... 20% 
    (Reading database ... 25% 
    (Reading database ... 30% 
    (Reading database ... 35% 
    (Reading database ... 40% 
    (Reading database ... 45% 
    (Reading database ... 50% 
    (Reading database ... 55% 
    (Reading database ... 60% 
    (Reading database ... 65% 
    (Reading database ... 70% 
    (Reading database ... 75% 
    (Reading database ... 80% 
    (Reading database ... 85% 
    (Reading database ... 90% 
    (Reading database ... 95% 
    (Reading database ... 100% 
    (Reading database ... 295120 files and directories currently installed.)
Removing oracle-java7-installer ...
update-alternatives: error: unknown argument `cdrom'
dpkg: error processing oracle-java7-installer (--remove):  subprocess installed pre-removal script returned error exit status 2
No apport report written because MaxReports is reached already
Downloading...
        --2012-04-12 13:13:21--  http://download.oracle.com/otn-pub/java/jdk/7u3-b04/jdk-7u3-linux-i586.tar.gz
Rsolution de download.oracle.com (download.oracle.com)...
        203.13.161.233, 203.13.161.234
Connexion vers download.oracle.com (download.oracle.com)|203.13.161.233|:80... connect. requte HTTP transmise, en attente de la rponse... 302 Moved Temporarily
Emplacement: https://edelivery.oracle.com/otn-pub/java/jdk/7u3-b04/jdk-7u3-linux-i586.tar.gz [suivant]
        --2012-04-12 13:13:21--  https://edelivery.oracle.com/otn-pub/java/jdk/7u3-b04/jdk-7u3-linux-i586.tar.gz
Rsolution de edelivery.oracle.com (edelivery.oracle.com)...
        173.223.150.174
Connexion vers edelivery.oracle.com (edelivery.oracle.com)|173.223.150.174|:443... connect. requte HTTP transmise, en attente de la rponse... 302 Moved Temporarily Emplacement: http://download.oracle.com/errors/download-fail-1505220.html [suivant]
        --2012-04-12 13:13:22--  http://download.oracle.com/errors/download-fail-1505220.html
Connexion vers download.oracle.com (download.oracle.com)|203.13.161.233|:80... connect. requte HTTP transmise, en attente de la rponse... 200 OK
Longueur: 5307 (5,2K) [text/html]
Sauvegarde en : ./jdk-7u3-linux-i586.tar.gz

             0K .....                                                 100% 4,94M=0,001s

        2012-04-12 13:13:22 (4,94 MB/s) - ./jdk-7u3-linux-i586.tar.gz sauvegard [5307/5307]

        Download done.
sha256sum mismatch jdk-7u3-linux-i586.tar.gz
Oracle JDK 7 is NOT installed.
dpkg: error while cleaning up:  subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:  oracle-java7-installer
Error in function:

I also tried "remove completely" from synaptic but it doesn't work either.

Thank you for your help in advance!