Sorry, but the problem has disappeared downgrading acpi-support, so I think is clearly related to this package.
** Changed in: acpi-support (Ubuntu) Status: Rejected => Unconfirmed -- kacpid-work eat 99% CPU after resuming from hibernate https://launchpad.net/bugs/56246 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs