Notebook inside aui.notebook blue strips

Hi,
If I run the attached sample in windows xp I see weird vertical and horizontal blue strips inside the notebook tab, they also slightly change when moving or maximizing.
Please have a look at it with high contrast on as the strips are a light blue.
Is it a bug?
Thanks all

PS: wxPython 2.8.7.1 - python 2.5.1 - unicode - windows xp

test.py (2.85 KB)