Download older versions of java jdk

It's the correct way to downgrade a package, but you seem to have got the version number wrong

apt-get install sun-java6-jdk=ubuntu1~ - won't work since there is no such package in the www.cronistalascolonias.com.ar list, that's why you got the error: Version ‘ubuntu1~’ for ‘sun-java6-jdk’ was not found.

Try this Removes the sun-java6-jdk

Download the .deb for your previous sun-java6-jdk version, you may already have this file in /var/cache/apt/archives use: in your terminal to find out whether you have an older version locally.

/ openjdkjdk -- the -d will only download the file into your /var/cache/apt/arhives folder.

(the version # that you have).

Lock Version in Synaptic so ubuntu doesn't try to upgrade it again. Dpkg man page will also help explain things -- downgrade has a big warning label on it in the man pages, so take note you don't wreck your dependencies. There is a post here and here that explains downgrading.