Are you still experiencing the issue? While I agree that the issue likely does have a cause, it is very difficult to determine the cause of these issues if they are not currently occurring. A clean logout could very well have enabled KDE to flush out the bad state responsible for this (which could have been KWin running in safe mode - ie. without desktop effects - for instance).

Issues are said to rectify themselves when circumstances change, or you make an otherwise apparently unrelated change which fixes the issue without you being aware of it. In most instances, what actually fixed it can't be identified.

I'm not still experiencing the issue.

I'm not meaning to argue. I just want to leave hints for the next person who stumbles across this problem and finds this thread. While there must be a cause and effect for everything, I agree that we won't know what the fix is, unless someone else with the same problem follows the same steps and it doesn't fix it for them. I think it's better to guess now what the fix was then for someone else to come along a month later and then try to guess. (btw, kwin was running with desktop effects.)

I'm thankful for the support I've received in this thread.

Sure - not a problem.
If this does come along again, hopefully we can find a solution to it.

just upgraded kde from 4.10.5 to 4.11.3 and the same problem is happening again. a clean leave and relogin didn't fix it this time. i also see that kde is not saving my session even though i have "restore previous session" "on login" enabled in "session management."

i have tried to kill kde processes one by one to see if restarting any of them fixes the issue, but so far only killing ksmserver (which causes me to log out) let's me recover control of X.

When you trigger the issue (of seeing applications updating, but not being able to interact with them) is there a "kscreenlocker" process running?
Not having your session saved is rather unusual, can you verify your user account owns and can write all files/directories under ~/.kde4?

There is not a kscreenlocker process. The last process to launch is plasma-overlay. `find ~/.kde -not -writable` returns nothing as unwritable.

If i'm not wrong, plasma-overlay is the process used for widgets on screensaver. Open System Settings > Display and Monitor > Screen Locker and ensure "Simple locker" has been selected as your desired type. Desktop Widgets should not be selected.

If Simple locker is already selected, change it to a regular screensaver and then back again to ensure any legacy configuration entries have been eliminated.

Thanks for that. I have been using "Desktop Widgets" as my screen locker type for years. "Simple locker" seems to lock the screen properly and seems like a reasonable workaround. Are there any settings I can clear so I can get "Desktop Widgets" working again? "Configure" "Desktop Widgets" seems to lock the screen properly, but Ctrl+Alt+L doesn't (when "Desktop Widgets" is selected).

Unfortunately i'm not sure. I would suggest trying out under a new user first before removing your local configurations however to verify it is a bug related to your configuration.

tracked it down to akonadi using mysql even though the package akonadi-backend-mysql wasn't installed (only akonadi-backend-sqlite was). on the qt4 side, only libqt4-sql-mysql was installed (no other qt4 database drivers). akonadi ended up crashing when it started. saving my session now also seems to work. not sure where it got the old session that it kept loading.