I have been experiencing identical random freezes on two different machines at two different locations:
Computer 1: This was running ubuntu 12.04 LTS with KDE and the freezes were very occasionally occuring. I upgraded to 15.04 (64 bit) with KDE and for a short while everything seemed fine. Plasma has become a pain however, so I switched back to unity, or whatever it is called now - "ubuntu" in the login screen. Lately the freezes have started occuring again though. Don't remember if they occured running KDE. They seem to have become more frequent after I installed lots of extra packages to get stuff like Dropbox, Wacom tablets and dual monitors working correctly. The machine froze at least once before those extra installs.
Processor: Intel Core i7 CPU 920 @ 2.67GHz x 8
Graphics: GeForce GTX 260/PCIe/SSE2
Kernel version 3.19.0-25-generic.
The freeze: Sometimes preceded by a short freeze, the pc will become unresponsive. Ctrl-Alt-Del, Ctrl-Alt-Backspace, Ctrl-Alt-F1 will not work. Can't remember if keeping a key pressed results in any sound responce. The mouse cursor will still move, but not click (or at least not show any sign of it). This goes for the Wacom tablet too.
The screen does not go blank or black, just remains as it was before the freeze. I often run Youtube on Chromium on a different workspace for music. That sometimes keeps playing and I think, but am not sure, that it sometimes stops after a short while. As it is not on my active workspace, I cannot see whether that is due to being preloaded or not. Also I don't know about the video, just the audio.
The freezes seem to be at random moments and I haven't been able to find a correlation with running any programs, though it sometimes seemed to result from playing with browser tabs. That may be coincidence though, as the freezes also seem to occur when no browser is open (not sure though, will start to keep better track from now on). EDIT It does indeed sometimes happen without and before any browser is loaded.
Computer 2: This pc does not share any hardware with computer 1. I had ubuntu 12.10 with KDE on it, and the freezes became so annoying that I decided to upgrade. This was no longer possible however, so I did a clean install of 15.04 (64-bit), keeping home folders intact. The pc is at another location and has a different ISP. On this pc I did not reinstall KDE and left it running as a "plain" ubuntu pc.
Processor: Intel Core i7-3770 CPU @ 3.40GHz x 8
Graphics: Gallium 0.4 on NVE7
Kernel version 3.19.0-25-generic.
The freeze: Identical to computer 1, which I find baffling, as I don't see other people reporting this and the computers have very little in common other than both having Wacom tablets, which are different models). I don't know if Youtube would keep playing on this machine - never use it here, though I do use Chromium here too.
What additional information can I provide to help solve this issue, and how do I go about getting it? Are there relevant logs to be found? Thanks for your help!
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