Several times over the past few weeks I've had my PC (Ubuntu 16.10*) apparently lock up: desktop stops changing (clock stops updating) but the mouse (usually) continues to move. Sometimes I can SSH in, although more often I can get as far as entering username/password but never reach a terminal prompt.
It can happen while I'm actively using it (mid-sentence), or if I go away and come back it could have locked in my absence, often relatively shortly after it was left (the stopped clock is quite handy...)
I found messages in syslog relating to nouveau so I replaced the graphics card (as a fairly cheap swap out). That made no difference (actually if anything it got worse, although I'd hesitate to say so for sure).
Rather than mess around I bought a new PC and transferred my system disk to it, still figuring it felt like a hardware issue. Except that the problem has followed across onto the new PC. The only things moved across are the new graphics card and three hard disks.
It no longer feels like a hardware issue....
How do I diagnose?
Or am I just looking at a re-install?
* Note that this PC has been upgraded through several versions, it wasn't a clear 16.10 install. The only "major" change recently has been a shift from Chrome to Opera as the primary browser (and since I tend to have dozens of tabs open and most of my work involves a browser in some way that does count as a major change).
Mark