Cannot use apt-get/dpkg -- Input/output error

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http://askubuntu.com – I have bumped into an issue that doesn't allow me to do anything related to apt-get: install, remove, etc. Whenever I try to do something (e.g. sudo apt-get install firefox -f) it gives me the same error message: Reading database ... dpkg: unrecoverable fatal error, aborting: unable to open files list file for package `fontconfig-config': Input/output error E: Sub-process /usr/bin/dpkg returned an error code (2) I have tried to deal with the package `fontconfig-config' without success. I have found that the "Input/output error" is usually linked with physical problems of the hd, but I do (HowTos)