Ubuntu 10.4 + Laptop. Display issues

[#1]

I'm pulling my hair out with this one, I've stuck Ubuntu on my laptop for my sister to use (rather than Vista) and it's not detecting my screen resolution properly, boot up gives the out of frequency/range issue of wiggly lines but I can get into Ubuntu at 800x600, I want 1280x800.
I've used xrandr which lists only 640x480 800x600, then I did cvt 1280x800 which produced the needed modelines.
I then did xrandr --newmode "1280x800_60.00" etc.. which should add the mode. So I type xrandr --output default 1280x800 and it complains "cannot find mode 1280x800" if I add the _60.00 on the end it also complains it can't find the mode.
I'm stumped, I wanted a nice easy Linux for my sister to use, and I can't install OpenSuSE 11.2 as my USB stick corrupted the ISO on my hard drive.
So, how do I get 1280x800 resolution?  The videocard is an SIS something or another, mirage 3?  Not sure.
/edit - ok, I got it added (I think) with xrandr --addmode default 1280x800_60.00 then tried xrandr --output default 1280x800_60.00 and it complained "screen cannot be larger than 800x600" argh, frustrating isn't the word.

[#2]

There appears to be some useful info in these threads on the ubuntuforums
http://ubuntu-ky.ubuntuforums.org/showthread.php?t=1439387
http://ubuntuforums.org/showthread.php?t=958967&page=38
That last one is quite a long thread...

[#3]

The 800 x 600 max. resolution makes me think X isn't detecting your graphics properly and falling back to using the vesa driver.
A quick trawl through /var/log/Xorg.O.log should confirm which driver X is loading.
You may have to revert to the good ol' fashioned /etc/X11/xorg.conf 

[#4]

Following those links I've installed the drivers as it were and get an error:
failed to load /usr/lib..../drivers/sis671_drv.so
failed to load module sis671 (loader failed, 7)
no drivers available
Fatal server error:
no screens found
Gah, this is hard work for a Saturday
/edit - it's tormenting me, I know it is, it's staring at me taunting me!  I downloaded the sources and ran ./configure and had dependants I needed to fix, managed to fix all them and ./configure ran, then make broke down.  The downloads don't work as they appear to be for x32 so you have to compile x64 and I can't compile x64 because the make breaks, I'm going around in circles, maybe my sister would like Vista? >.<
/edit 2 - finally! Success.
As this may hit google....  I downloaded the sources from here  and installed the required dependencies as well as mesa devel and gl proto, without those it wouldn't compile.  Make still crashed out when trying to compile the man folder but that wasn't an issue, I cd'd into src/.lib and in there are the driver files which I copy to /usr/lib/xorg/modules/drivers/ and follow the tutorial from here to complete
Driver files are sis671_drv.la and sis671_drv.so
Now it's all looking nice at 1280x800 and my sister can learn Linux