.xsession-errors filled up by debug messages

[Suppositoire <suppositoire@no-log.org>]

Hello,

I'm experiencing some problems when setting Menus effect to transparent 
(defined in kcontrol / KDE Style Effects), since it fills up my 
~/.xsession-errors with debug messages like :

QImage::setPixel: x=0 out of range
QImage::setPixel: x=0 out of range
QImage::setPixel: x=0 out of range
(...)
QImage::setPixel: x=1 out of range
QImage::setPixel: x=1 out of range
QImage::setPixel: x=1 out of range
(...)
QImage::setPixel: x=2 out of range
QImage::setPixel: x=2 out of range
QImage::setPixel: x=2 out of range
(...)
etc.

Config :
Debian Sid up-to-date
kernel 2.6.22-3-686
KDE 3.5.8
Theme and Style : Polyester (verified on Plastik too)

Regards.