I post this in window-list widget, but it is just the window widget of plasma. It was not possible to select in the bugtracker the correct one (not existent) ..

At least for the case, that the alignment is perpendicular: 
- the alignment of the windows is sometimes broken
 * Two windows drawn in one row (no selection possible)
 * free space at the top of the widget (dislocation of all windows)
- It is not dependent on the program. Just eclipse + dolphin fails also


This bug is already very old in KDE4 (at least in OpenSuse), reproduced by many users and I get personally more and more annoyed. 
Even made a picture which proves the problem: http://oi40.tinypic.com/20f5egx.jpg



Reproducible: Sometimes

Steps to Reproduce:
1. Work with many (at least two opened) windows
2. Perpendicular window widget
3. 2. 1. : FAIL


Expected Results:  
Correct window alignment

http://oi40.tinypic.com/20f5egx.jpg