In my KDE 4.7.4, sometimes the panels freeze for ~10 seconds. During that period, all input is ignored (can't open start menu, switch to another window, switch desktop etc.) Keyboard shortcuts continue to work, that means I can still switch window with ALT+TAB, switch desktop etc.

I suspect one of the apps in tray be be the reason (Skype, Dropbox, Amarok etc), but how can I find out which one it is?

if there are no apps in the system tray, there is no freezing?

you could try process of elimination, remove apps until it longer freezes, I would focus on non-KDE apps as those would most likely not play nice (Skype particularly)

Somehow this seems to not be deterministic. Sometimes there's no freeze with all apps (I regularly use) open, sometimes the problem persists even when closing all of them.
Maybe it's related with this issue I have: viewtopic.php?f=66&t=99811&p=215596#p215596

have you tried disabling effects?

if you create and login as a new user does this still happen?

could you upgrade to 4.8?

I will try to disable effects the next time this happens.

Since it doesn't happen very often (and I didn't find a way to reproduce it yet) it's difficult to check with a different user (how long to test until I can say there's no problem?)

I won't ugrade to 4.8 before Ubuntu 12.04 is released. Need to work on this machine daily, so I can't afford to risk any breakage.

normally when checking if it's an effects problem you disable effect and if it doesn't occur you start adding effects back until it happens again

is only the input on the panel blocked (ie you can still click into another window to activate it, type and click buttons there, etc.) or does mouse input not work globally but keyboard does?

In case it's only the panel, some plasmoid is running wild (or rather blocking the GUI thread, probably waiting for some I/O - got a battery applet in there?) - otherwise sth. has grabbed the pointer (you can check that by attempting to run "xprop" from konsole)

luebking wrote:In case it's only the panel, some plasmoid is running wild (or rather blocking the GUI thread, probably waiting for some I/O - got a battery applet in there?) - otherwise sth. has grabbed the pointer (you can check that by attempting to run "xprop" from konsole)

Yes, it's only the panel.
I have only default (preconfigured) plasmoids running (kmix, update notification, battery status etc.), except one cpu monitor.

The strange thing is that the issue comes and goes. For example now I'm working for about 10 hrs without a single freeze. Yesterday I had the freezes (around 20 seconds) every 20 minutes or so. As far as I can see, the same applications are running. The only thing that changed was a reboot in between.

I'm only aware of two applets which may be causing this issue, the Network Management applet and the Battery applet.

If you remove them, can you reproduce this issue?