Comment 14 for bug 107711

I find your log output most interesting.

Someone who understands the X configuration better than I should work on the question,
"Why does the EDID data CLEARLY offer details for operation at 1280x800, but the X server configure itself down to 800x600?"

The particular problem I'm working on has to do with the question, "How much of the EDID data block really SHOULD be coming up zeros?"

If you look at your log output, you see the lines beginning, "EDID (in hex):"

Those 128 bytes should ALWAYS be the same. If you're being bitten by the same bug that bites me, you will see them coming up randomly DIFFERENT with successive runs of the X server.
This has the effect of only providing a partial fill-in of the data X wants in order to successfully configure the monitor.

Something for you to try: Restart the X server several times, and watch that EDID output.
See if it changes.

Something that might get you going is to see if, in xorg.conf, you have 1280x1024 and 1024x768 in the "Modes" subsection of your "Screen" section, looking something like this:

        SubSection "Display"
                Depth 24
                Modes "1280x1024" "1152x864" "1024x768" "800x600" "640x480"
        EndSubSection

Maybe you're being bit by the bug I will get bit by in the FUTURE when the EDID transfer becomes successful, but the X server mis-applies the data.