Multiple Monitors and Screen Resolution
 

Now this should (in theory) be an easy thing.
On KDE 4.7 on Arch Linux (x86_64) I've set up a nice, KDE desktop using two monitors. One is widescreen, one is not.

The widescreen monitor has its resolution set perfectly, whether the other monitor is plugged in or not. Since it's the primary screen, unsurprising.
However, the other monitor is proving to be a pest. It's capable of 1280x1024 resolution, which has worked fine in the past, but now is apparently unsupported and thus KDE's display management does not show it.
It won't let me pick anything above 1024x768, and for that matter neither will any other GUI app for handling it.

Command line ones work, but never seem to hold through a reboot, forcing a manual re-application - and even then, if one enters the KDE display management, it gets forced back to 1024x768.

So now, how do I tell KDE that the second screen really can support that screen size, so I can select and use it again?

Can you manually specify the resolution in xorg.conf??

Quite probably - if I had one. Since the option to have it auto-generated on each use, this particular PC has never needed an xorg.conf file.

Edit: Thanks to persistent searching, the actual problem as been found.
It was suggested to run the command:
'xrandr --output VGA1 --mode 1280x1024'
to forcibly set it. However, this outputs:
xrandr: cannot find mode 1280x1024

Which is most peculiar, since even a (K)Ubuntu LiveCD will let me pick that resolution, but Arch's KDE does not.