I have the same issue with similar kern.log entries after upgrading to kernel 3.16.0-48. Removing that and falling back to 3.16.0-46 fixed it for me.
** Attachment added: "Excerps from kern.log, lshw, ifconfig" https://bugs.launchpad.net/ubuntu/+source/linux-lts-utopic/+bug/1492146/+attachment/4457713/+files/log_lshw_ifconfig.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1492146 Title: igb Detected Tx Unit Hang To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-lts-utopic/+bug/1492146/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
