iBook: dual head

[Krischan]

Hello list,

i am runding ydl 3.0.1 with kernel 2.6.7 and XFree86 (4.4) on an iBook
(g3 800MHz, ATI Radeon Mobility M7 LW 7500).

I conected an external LCD monitor with the vga adaptor to use the
dualhead option with xinerama support. The external LCD runs with
1280x1024 and the iBook screen with 1024x786 resolution. 

It works - BUT _some_ of the colors look strange: Icons and window
decorations have a yellow touch. 

Has anyone an idea why this happens? Where do I need to look at? Any
hints are apprechiated. Thanks a lot!

Krischan