The KM400 video card is reported as unrecognised, the s3virge card BIOS cannot be read, in the following log. Note that the recognition of the KM400 is patchy - some sections seem to see it correctly. Error lines, excerpted from full log: (EE) VIA(0): Unknown Card-Ids (1043|80F9), report this to the driver maintainer ASAP (EE) S3VIRGE(1): Cannot read V_BIOS Needless to say, the result is a black screen, and one must reboot to get out. Complete log attached.
Created attachment 95086 [details] Full log of failed Xorg session
This should be fixed in 7.1 if you'd like to use the ~arch xorg-server and drivers. It's purely an issue on dual-head systems. To reassure you, they're not ~arch because they're unstable but because we haven't yet stabilized compatible binary drivers.
Thanks Donnie, works perfectly.