It seems that a lot of GPU problems revolve around specific versions of drivers. Though NVidia has their own support structure, you can often learn from information reported by others who fold.
bollix47 wrote:On Ubuntu 13.04 I'm using nvidia-319 from xorg-edgers and my GTX 780 appears to be working well.
That did the trick ... I tried several times to reinstall 12.04 and 13.04 with driver from nvidia or standard repo. Funny, the card get even identified as Titan.
Finally I tried your suggestion with the alternative repo and it worked directly. Actually with that one I even will try again VMware and ESXi passthrough; I got similar messages there. Thanks for the tip !
The patch has not been applied to the Linux version. The user has to manually place GPUs.txt into the fahclient's home folder. Even doing that is not helping because in a few seconds the Queue for the GPU reports