Help. I can't help myself. I've read many similar issues but without luck. I did memtest, autoclean, I even enabled only single core just to be sure it's not some way of concurrency issue.

Right now I've installed 3.13.0-83 kernel as I believe it was the one I've used without any problems before all this troubles.

Below is my apt history which can be treated like suspect as it was last installs before problem appeared. However I didn't find any critical package here (like lvm, luks) but maybe one of you will find something strange:

Commandline: apt-get install --reinstall skype
Install: skype:amd64 (4.2.0.11-0ubuntu0.12.04.2), libdbusmenu-qt2:i386 (0.9.3+14.04.20140314-0ubuntu1, automatic), skype-bin:i386 (4.2.0.11-0ubuntu0.12.04.2,
 automatic), sni-qt:i386 (0.2.6-0ubuntu1, automatic)
End-Date: 2016-05-09  19:35:39

Start-Date: 2016-05-09  19:47:41
Commandline: apt-get install --reinstall libgl1-mesa-glx:i386
Reinstall: libgl1-mesa-glx:amd64 (10.1.3-0ubuntu0.6), libgl1-mesa-glx:i386 (10.1.3-0ubuntu0.6)
End-Date: 2016-05-09  19:47:44

Start-Date: 2016-05-09  19:57:51
Commandline: apt-get purge skype
Purge: skype:amd64 (4.2.0.11-0ubuntu0.12.04.2)
End-Date: 2016-05-09  19:57:52

Start-Date: 2016-05-10  19:19:59
Commandline: apt-get -y purge linux-headers-3.13.0-83 linux-headers-3.13.0-83-generic linux-image-3.13.0-83-generic linux-image-extra-3.13.0-83-generic
Purge: linux-image-extra-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-image-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-headers-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-headers-3.13.0-83:amd64 (3.13.0-83.127)
End-Date: 2016-05-10  19:20:54

Start-Date: 2016-05-10  19:28:47
Commandline: apt-get dist-upgrade -y
Install: linux-image-extra-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic), linux-image-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic), linux-headers-3.13.0-86:amd64 (3.13.0-86.130, automatic), linux-headers-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic)
Upgrade: linux-headers-generic:amd64 (3.13.0.85.91, 3.13.0.86.92), liblcms2-2:amd64 (2.5-0ubuntu4, 2.5-0ubuntu4.1), python-samba:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), openssh-server:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), openssh-sftp-server:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), libtevent0:amd64 (0.9.26-0ubuntu0.14.04.1, 0.9.28-0ubuntu0.14.04.1), openjdk-7-jdk:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), klibc-utils:amd64 (2.0.3-0ubuntu1, 2.0.3-0ubuntu1.14.04.1), openjdk-7-jre-headless:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), samba-common-bin:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), ssh:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), samba-libs:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), openssh-client:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), openjdk-7-jre:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), openjdk-7-source:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), libklibc:amd64 (2.0.3-0ubuntu1, 2.0.3-0ubuntu1.14.04.1), icedtea-7-jre-jamvm:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), linux-doc:amd64 (3.13.0-85.129, 3.13.0-86.130), libwbclient0:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), linux-libc-dev:amd64 (3.13.0-85.129, 3.13.0-86.130), linux-libc-dev:i386 (3.13.0-85.129, 3.13.0-86.130), samba-common:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), linux-image-generic:amd64 (3.13.0.85.91, 3.13.0.86.92), libsmbclient:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), libmms0:amd64 (0.6.2-3ubuntu2, 0.6.2-3ubuntu2.1), linux-generic:amd64 (3.13.0.85.91, 3.13.0.86.92)
End-Date: 2016-05-10  19:32:19

Start-Date: 2016-05-12  21:21:55
Commandline: apt-get dist-upgrade -y
Upgrade: libnl-genl-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), libnl-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), lsb-base:amd64 (4.1+Debian11ubuntu6, 4.1+Debian11ubuntu6.1), lsb-release:amd64 (4.1+Debian11ubuntu6, 4.1+Debian11ubuntu6.1), libnm-util2:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), libnm-glib-vpn1:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), network-manager:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), libnl-route-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), libnm-glib4:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3)
End-Date: 2016-05-12  21:22:17

Start-Date: 2016-05-12  21:23:13
Commandline: apt-get purge linux-generic
Purge: linux-generic:amd64 (3.13.0.86.92)
End-Date: 2016-05-12  21:23:14Commandline: apt-get install --reinstall skype
Install: skype:amd64 (4.2.0.11-0ubuntu0.12.04.2), libdbusmenu-qt2:i386 (0.9.3+14.04.20140314-0ubuntu1, automatic), skype-bin:i386 (4.2.0.11-0ubuntu0.12.04.2,
 automatic), sni-qt:i386 (0.2.6-0ubuntu1, automatic)
End-Date: 2016-05-09  19:35:39

Start-Date: 2016-05-09  19:47:41
Commandline: apt-get install --reinstall libgl1-mesa-glx:i386
Reinstall: libgl1-mesa-glx:amd64 (10.1.3-0ubuntu0.6), libgl1-mesa-glx:i386 (10.1.3-0ubuntu0.6)
End-Date: 2016-05-09  19:47:44

Start-Date: 2016-05-09  19:57:51
Commandline: apt-get purge skype
Purge: skype:amd64 (4.2.0.11-0ubuntu0.12.04.2)
End-Date: 2016-05-09  19:57:52

Start-Date: 2016-05-10  19:19:59
Commandline: apt-get -y purge linux-headers-3.13.0-83 linux-headers-3.13.0-83-generic linux-image-3.13.0-83-generic linux-image-extra-3.13.0-83-generic
Purge: linux-image-extra-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-image-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-headers-3.13.0-83-generic:amd64 (3.13.0-83.127), linux-headers-3.13.0-83:amd64 (3.13.0-83.127)
End-Date: 2016-05-10  19:20:54

Start-Date: 2016-05-10  19:28:47
Commandline: apt-get dist-upgrade -y
Install: linux-image-extra-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic), linux-image-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic), linux-headers-3.13.0-86:amd64 (3.13.0-86.130, automatic), linux-headers-3.13.0-86-generic:amd64 (3.13.0-86.130, automatic)
Upgrade: linux-headers-generic:amd64 (3.13.0.85.91, 3.13.0.86.92), liblcms2-2:amd64 (2.5-0ubuntu4, 2.5-0ubuntu4.1), python-samba:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), openssh-server:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), openssh-sftp-server:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), libtevent0:amd64 (0.9.26-0ubuntu0.14.04.1, 0.9.28-0ubuntu0.14.04.1), openjdk-7-jdk:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), klibc-utils:amd64 (2.0.3-0ubuntu1, 2.0.3-0ubuntu1.14.04.1), openjdk-7-jre-headless:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), samba-common-bin:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), ssh:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), samba-libs:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), openssh-client:amd64 (6.6p1-2ubuntu2.6, 6.6p1-2ubuntu2.7), openjdk-7-jre:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), openjdk-7-source:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), libklibc:amd64 (2.0.3-0ubuntu1, 2.0.3-0ubuntu1.14.04.1), icedtea-7-jre-jamvm:amd64 (7u95-2.6.4-0ubuntu0.14.04.2, 7u101-2.6.6-0ubuntu0.14.04.1), linux-doc:amd64 (3.13.0-85.129, 3.13.0-86.130), libwbclient0:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), linux-libc-dev:amd64 (3.13.0-85.129, 3.13.0-86.130), linux-libc-dev:i386 (3.13.0-85.129, 3.13.0-86.130), samba-common:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), linux-image-generic:amd64 (3.13.0.85.91, 3.13.0.86.92), libsmbclient:amd64 (4.3.8+dfsg-0ubuntu0.14.04.2, 4.3.9+dfsg-0ubuntu0.14.04.1), libmms0:amd64 (0.6.2-3ubuntu2, 0.6.2-3ubuntu2.1), linux-generic:amd64 (3.13.0.85.91, 3.13.0.86.92)
End-Date: 2016-05-10  19:32:19

Start-Date: 2016-05-12  21:21:55
Commandline: apt-get dist-upgrade -y
Upgrade: libnl-genl-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), libnl-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), lsb-base:amd64 (4.1+Debian11ubuntu6, 4.1+Debian11ubuntu6.1), lsb-release:amd64 (4.1+Debian11ubuntu6, 4.1+Debian11ubuntu6.1), libnm-util2:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), libnm-glib-vpn1:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), network-manager:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3), libnl-route-3-200:amd64 (3.2.21-1, 3.2.21-1ubuntu1), libnm-glib4:amd64 (0.9.8.8-0ubuntu7.2, 0.9.8.8-0ubuntu7.3)
End-Date: 2016-05-12  21:22:17