Version:           unspecified (using KDE 4.5.95) 
OS:                Linux

This is most easily noticeable on the plasma widgets, such as the menu, networking widget and power widget.  As the widgets are sliding up, blur is not applied.  Once they are fully extended, then the blur is applied.

Reproducible: Always

Steps to Reproduce:
set kwin animation speed to slow if you need to see it better.  Open the networking plasmoid or battery plasmoid.  

Actual Results:  
Blur is not applied until the widget is fully extended.

Expected Results:  
Blur should be applied throughout the animation.

This also applies to ARGB QT styles, such as Oxygen transparent or Bespin.  The blur is only applied to non-moving windows.