BTW, does video work fine? Can you post the output of "xrandr -q"?

nouveau  [     DRM] allocated 640x400 fb: 0x60000, bo f4cf1800

But your monitor can probably do a bit more than 640x400, which indeed points
to a potential EDID problem parsing problem. (I also don't see 640x400 as one
of the modes reported by X.) Normally it picks the native resolution of your
monitor... do you have something on cmdline that overrides that? Normally
there's a Command line: printed in the dmesg, but yours doesn't have it.
Perhaps that happens when the cmdline is empty...

Lastly, is this a x86_32 kernel? Can't imagine it'd matter, but good to know in
any case. (I guess it is since you mention i686, but kernel can still be x86_64
in that case.)