I uninstalled Xorg, rebooted, and then re-installed it from the console using "tce-load -wi Xorg-7.6". Everything appeared to download fine. Then I typed "sudo su", hit enter, "Xorg -configure", hit enter, then typed "startx", hit enter again, and got the familiar "No video signal" on my monitor's OSD. Ctrl+Alt+Del was unable to break me out of it, so I had to restart, and I'm back with the same 1024x768 resolution as before.
In the xorg.conf (the version which I've edited), I've specified 1280x1024 as a resolution, and a refresh rate of 60Hz. According to my monitor's specs, 1280x1024@60 is an accepted resolution/refresh.
I'm finding it hard to track down Xorg config info pitched at the right level for me on the web, and there seem to be different ways of configuring the same property to achieve the same result, so do please bear with me if there's anything obvious I'm failing to mention or do.
In case my monitor is the source of these problems, I've managed to find some more detailed specs for it, including a mode line, but I believe, from what I've read, that inputting the wrong info into a xorg.conf can permanently damage a monitor, so I'm wary of trying anything along those lines. That said, if my monitor is part of the problem, maybe I just need a different monitor...
Many thanks, Jon.