Description of problem:
Under KDE, when the cursor is on the panel, and the windows are transparent, I got some freezes. The only method available is to stop the machine with OFF button.
In syslog, I get :
Jul  3 22:24:03 localhost kernel: [ 1969.308657] [drm] nouveau 0000:00:0d.0: error fencing pushbuf: -16 
Jul  3 22:24:47 localhost kernel: [ 2013.839250] [drm] nouveau 0000:00:0d.0: fail post-validate sync 
Jul  3 22:24:47 localhost kernel: [ 2013.839260] [drm] nouveau 0000:00:0d.0: validate both_list 
Jul  3 22:24:47 localhost kernel: [ 2013.839290] [drm] nouveau 0000:00:0d.0: validate: -16 


lspcidrake |grep DISPLAY
Card:NVIDIA GeForce 6100 to GeForce 360: nVidia Corporation|C61 [GeForce 7025 / nForce 630a] [DISPLAY_VGA] (rev: a2)

Yves