Screen resolution only 1024x768 in Acer Aspire One ZA3. 16:9 not supported

Acer Aspire One ZA3 netboook has a 16:9 1280x768 screen.
But Ubuntu 9.10 only detect 4:3 1024x768, 700x600 screen resolutions.

ProblemType: Bug
Architecture: i386
CheckboxCommand: xrandr
CheckboxData: maximum: 1280 x 768
CheckboxDescription:
 Se han detectado en su sistema las siguientes pantallas y modos de vídeo:

 $output

 ¿Es ésto correcto?
CheckboxTest: xrandr_detect_modes
Date: Sat May 1 18:19:38 2010
DistroRelease: Ubuntu 9.10
LiveMediaBuild: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
MachineType: Acer AO751h
Package: x11-xserver-utils 7.4+2ubuntu3
ProcCmdLine: BOOT_IMAGE=/casper/vmlinuz noprompt cdrom-detect/try-usb=true persistent file=/cdrom/preseed/hostname.seed boot=casper initrd=/casper/initrd.lz quiet splash -- debian-installer/language=es console-setup/layoutcode?=es
ProcEnviron:
 SHELL=/bin/bash
 LANG=es_ES.UTF-8
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
RelatedPackageVersions:
 xserver-xorg 1:7.4+3ubuntu7
 libgl1-mesa-glx 7.6.0-1ubuntu4
 libdrm2 2.4.14-1ubuntu1
 xserver-xorg-video-intel 2:2.9.0-1ubuntu2
 xserver-xorg-video-ati 1:6.12.99+git20090929.7968e1fb-0ubuntu1
SourcePackage: x11-xserver-utils
Tags: checkbox-bug
Uname: Linux 2.6.31-14-generic i686
XorgConf: Error: [Errno 2] No existe el fichero ó directorio: '/etc/X11/xorg.conf'
dmi.bios.date: 04/27/2009
dmi.bios.vendor: Acer
dmi.bios.version: V0.3202
dmi.board.name: JV11-ML
dmi.board.vendor: Acer
dmi.board.version: Not Applicable
dmi.chassis.type: 1
dmi.chassis.vendor: Acer
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAcer:bvrV0.3202:bd04/27/2009:svnAcer:pnAO751h:pvrNotApplicable:rvnAcer:rnJV11-ML:rvrNotApplicable:cvnAcer:ct1:cvrN/A:
dmi.product.name: AO751h
dmi.product.version: Not Applicable
dmi.sys.vendor: Acer
fglrx: Not loaded
system:
 distro: Ubuntu
 architecture: i686kernel: 2.6.31-14-generic