I have a SiS 761GX board and the symptom is the same. Ubuntu uses by default an odd resolution to my CRT monitor, 960x600, and 1024x768 isn't available (despite being supported). The main problem should be the DDC support broken of sis driver.
I found this old Debian bug, probably related: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=473134 My Xorg log has these lines: (II) SIS(0): VESA VBE DDC read failed ... (II) SIS(0): Replaced entire mode list with built-in modes Using another machine, with an i945G chip, plugged in the same monitor, all works ok. The resolutions are correctly configured (uses 800x600 by default) and I have 1024x768 as an option. I'm attaching my log. ** Bug watch added: Debian Bug tracker #473134 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=473134 ** Attachment added: "Xorg.0_SIS.log" http://launchpadlibrarian.net/48606161/Xorg.0_SIS.log -- GRAFIC HARDWARE NO SUPPORT UBUNTU BUG RESOLUTIONN https://bugs.launchpad.net/bugs/577871 You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-sis in ubuntu. _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp