Version:           unspecified (using KDE 4.6.2) 
OS:                Linux

When "Effect for windows switching" is set to be FlipSwitch, there is about a 1/3 chance that all KWin hangs up, blocking input. (The only way go is Ctrl-Alt-F1). Even if it didn't, there is the same chance to hang up when using Alt-Tab, pressing it briefly. However, no bugs occur when Alt-Tab is pressed and hoild to see the FlipSwitch animation. 


Reproducible: Always

Steps to Reproduce:
1) Go System Settings -> Desktop Effects. Set "Effect for window switching" to FlipSwitch. 
2)Open a few windows. Press and hold Alt-Tab. Everything works.
3)Press Alt-Tab momentarily several times. Everything hangs.

Actual Results:  
No way to recover found. Key combo that stops desktop effects don't work. Restart your X server. 

Expected Results:  
It seems that when Alt-Tab is pressed for a moment, the animation does not start, does it? Windows should just switch.

That didn't happen in previous versions of KDE on that machine. I have the latest nvidia prop drivers (270.41.06)