I just did a dist-upgrade (xserver-xorg-video-vesa 1:1.2.1-3 -> 1:1.3.0-1) and the error does not appear anymore.
Tested with 1600x1200, 1280x1024, 1024x768 on Linux 2.6.18-3-amd64. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]