Re: Xorg, Nvidia -> black screen of death.
1. /usr/src/linux is linked to the proper kernel when I install it. And yes, after installing each kernel I've re-emerged nvidia-kernel nvidia-glx and ran opengl-update nvidia.
2. Turning ACPI off causes my system not to see the AGP.
3. I've tried passing the nopapic kernel parameter, no difference.
Executing an 'emerge -p linux-headers' showed that for some reason there was an update/change that should have taken place but didn't. I've run that and am now re-emerging glibc as per the header instructions. I'll then recompile/install my kernel and nvidia drivers and see if this makes a difference. Hopefully it will, thanks for the idea.
4. I didn't check to see if the previous version of the drivers properly used agp, but with them I definitely couldn't turn on ACPI which results in not being able to auto power off the box on shutdown.