[gentoo-user] xorg-x11, why hath thou forsaken my 2nd screen?

[Phill MV]

In a haste to get the latest gnome-light packages, I ran
ACCEPT_KEYWORDS="~x86" emerge -Duva world without thinking about the
consequences and ended up running an 'unmasked' system.
Now, this is okay. I'll just wait till said packages go into the stable
depository or downgrade or something.

In the meanwhile, it'd be really grand if I could use my 2nd screen.
Running etc-update and scrolling through the 50 or so new conf files, I was
careful enough not to have my xorg.conf overwritten; one moment it's
working, a quick reboot later (revealing a whole bunch of other cock-ups I
might spend another email detailing) and only my main screen starts up.

Now, this is baffling. Opening my xorg.conf shows me my xinerama, dual
screen setup clearly detailed the way I like it. Nothing has changed - yet
no errors show up when starting X, no confusing flickers of the 2nd monitor,
no hardwarming hard crashes, nothing. It's as if it just forgot all about
that silly mess and went on with it's life, making me use my main screen as
if nothing ever happened.

Any suggestions or places I should look in?
(yes, xinerama is a use flag I use)