Must be video card related.
yeah maybe

well:
"Your machine does not support per pixel borders on WindowBlinds skins.
This is because :
Your computer graphics hardware does not support acceleration of per pixel alpha. WindowBlinds requires this for per pixel alphablended borders as without it performance would be poor. Please see if you can obtain new drivers for your graphics hardware. Recent ATI & NVIDIA boards should support this feature. Onboard graphics tend not to.
It appears you have enabled limited per pixel mode, so WindowBlinds will support per pixel, but with no hardware support.
(Écran Plug-and-Play) 1 is attached to GIGABYTE RADEON 9200"
Really Odd cause perpixel work perfectly here