[clug] KDE desktop kinda freezing

[Tony Lewis]

I've been running the current Kubuntu version for the last few months, 
and I find that every so often it freezes.  I'm trying to find out what 
causes it and what I can do to fix it.

The symptoms are:

  * the mouse cursor moves freely, but no actions do anything to windows
  * the keyboard does nothing
  * the desktop doesn't change, including panels with clocks in it
  * audio keeps playing (e.g. spotify)
  * I cannot successfully save my Windows VM from the command line (more
    below)

I can switch to text consoles, log in and do stuff.  Nothing unusual is 
showing up in htop (i.e. no excessive disk or CPU usage, no excessive 
memory, no meaningful swapping).

Things I've tried:

  * killing processes like the obvious contenders (for me) of Firefox,
    Thunderbird and VirtualBox
  * killing and restarting plasmashell
  * looking for other desktopy processes and killing them
  * starting an xterm from the command line into the desktop -
    'DISPLAY=:0.0 xterm' - from the command line it looks like it
    starts, but no change to the desktop

The worst part of this is any loss of documents in my work Windows VM, 
where I am not diligent in saving documents sometimes.  I try the 
'savestate' command, which works under normal circumstances, but under 
this frozen desktop scenario, it doesn't complete; it freezes up 
somewhere between 90 and 100% even if I leave it for hours.

Eventually I have to pretty much just restart.

What can I do to try and debug?

Tony