according to last comments, have you tried to upgrade your system with last ubuntu version? because I think this problem was solved, please check and comment if this issue was fixed.
** Package changed: ubuntu => linux (Ubuntu) -- Volume keys on Lenovo laptop not mapped to system Volume https://bugs.launchpad.net/bugs/347160 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
