The recent problem faced by me was that suddenly after an online update my computer went too slow….i could feel the zagginess while while moving windows. After using “ctrl+esc” i realized that Xorg was using a lot of CPU % which didnt come below 25% n every thing was getting slow coz of it. I though it was due to some problem in compiz or Xorg n will vanish after one or two updates but that didn’t happen so it striked to me that it must be due to some plugin so i turned off all the plugins n every thing was normal again 
I started to turn on each plugin one by one and observe the changes n i saw that blur plugin was on but its own n it was causing the problem and also the reflection plugin was causing the problem ( well i dont have a graphics card n if u do maybe reflection plugin wont make a difference i think) so u can try this n if even this doesnt solve the problem try switching off the KDE4 native effects. Hope this will solve the similar problem faced by any of u
